widgets(table): implemented selectable rows

- Implemented `TableContext.sel_rows`, allowing users to specify which rows have been 'selected' (similar to ctrl+clicking items in a GUI file browser).
- Changed previous 'selected' verbiage to 'active' in all cases.

examples/table.zig

···
     defer cmd_input.deinit();
 
     // Colors
-    const selected_bg: vaxis.Cell.Color = .{ .rgb = .{ 64, 128, 255 } };
+    const active_bg: vaxis.Cell.Color = .{ .rgb = .{ 64, 128, 255 } };
+    const selected_bg: vaxis.Cell.Color = .{ .rgb = .{ 32, 64, 255 } };
     const other_bg: vaxis.Cell.Color = .{ .rgb = .{ 32, 32, 48 } };
 
     // Table Context
-    var demo_tbl: vaxis.widgets.Table.TableContext = .{ 
+    var demo_tbl: vaxis.widgets.Table.TableContext = .{
+        .active_bg = active_bg,
         .selected_bg = selected_bg,
         //.col_width = 10,
+        //.y_off = 10,
     };
+    defer if (demo_tbl.sel_rows) |rows| alloc.free(rows);
 
     // TUI State
     var active: ActiveSection = .mid;
···
                         // Change Column
                         if (key.matchesAny(&.{ vaxis.Key.left, 'h' }, .{})) demo_tbl.col -|= 1;
                         if (key.matchesAny(&.{ vaxis.Key.right, 'l' }, .{})) demo_tbl.col +|= 1;
+                        // Select/Unselect Row
+                        if (key.matches(vaxis.Key.space, .{})) {
+                            const rows = demo_tbl.sel_rows orelse createRows: {
+                                demo_tbl.sel_rows = try alloc.alloc(usize, 1);
+                                break :createRows demo_tbl.sel_rows.?;
+                            };
+                            var rows_list = std.ArrayList(usize).fromOwnedSlice(alloc, rows);
+                            for (rows_list.items, 0..) |row, idx| {
+                                if (row != demo_tbl.row) continue;
+                                _ = rows_list.orderedRemove(idx);
+                                break;
+                            }
+                            else try rows_list.append(demo_tbl.row);
+                            demo_tbl.sel_rows = try rows_list.toOwnedSlice();
+                        }
                     },
                     .btm => {
                         if (key.matchesAny(&.{ vaxis.Key.up, 'k' }, .{}) and moving) active = .mid
···
             .width = .{ .limit = win.width },
             .height = .{ .limit = 1 },
         });
-        if (active == .btm) bottom_bar.fill(.{ .style = .{ .bg = selected_bg } });
+        if (active == .btm) bottom_bar.fill(.{ .style = .{ .bg = active_bg } });
         cmd_input.draw(bottom_bar);
 
         // Render the screen

src/widgets/Table.zig

···
 
 /// Table Context for maintaining state and drawing Tables with `drawTable()`.
 pub const TableContext = struct {
-    /// Current selected Row of the Table.
+    /// Current active Row of the Table.
     row: usize = 0,
-    /// Current selected Column of the Table.
+    /// Current active Column of the Table.
     col: usize = 0,
     /// Starting point within the Data List.
     start: usize = 0,
+    /// Selected Rows.
+    sel_rows: ?[]usize = null,
 
     /// Active status of the Table.
     active: bool = false,
 
-    /// The Background Color for Selected Rows and Column Headers.
+    /// The Background Color for the Active Row and Column Header.
     selected_bg: vaxis.Cell.Color,
+    /// The Background Color for Selected Rows.
+    active_bg: vaxis.Cell.Color,
     /// First Column Header Background Color
     hdr_bg_1: vaxis.Cell.Color = .{ .rgb = [_]u8{ 64, 64, 64 } },
     /// Second Column Header Background Color
···
     if (table_ctx.col > headers.len - 1) table_ctx.*.col = headers.len - 1;
     for (headers[0..], 0..) |hdr_txt, idx| {
         const hdr_bg =
-            if (table_ctx.active and idx == table_ctx.col) table_ctx.selected_bg else if (idx % 2 == 0) table_ctx.hdr_bg_1 else table_ctx.hdr_bg_2;
-        const hdr_win = table_win.initChild(
-            idx * table_ctx.col_width,
-            0,
-            .{ .limit = table_ctx.col_width },
-            .{ .limit = 1 },
-        );
-        var hdr = vaxis.widgets.alignment.center(hdr_win, @min(table_ctx.col_width -| 1, hdr_txt.len +| 1), 1);
+            if (table_ctx.active and idx == table_ctx.col) table_ctx.active_bg else if (idx % 2 == 0) table_ctx.hdr_bg_1 else table_ctx.hdr_bg_2;
+        const hdr_win = table_win.child(.{
+            .x_off = idx * col_width,
+            .y_off = 0,
+            .width = .{ .limit = col_width },
+            .height = .{ .limit = 1 },
+        });
+        var hdr = vaxis.widgets.alignment.center(hdr_win, @min(col_width -| 1, hdr_txt.len +| 1), 1);
         hdr_win.fill(.{ .style = .{ .bg = hdr_bg } });
         var seg = [_]vaxis.Cell.Segment{.{
             .text = if (hdr_txt.len > table_ctx.col_width and alloc != null) try fmt.allocPrint(alloc.?, "{s}...", .{hdr_txt[0..(table_ctx.col_width -| 4)]}) else hdr_txt,
···
     end = table_ctx.*.start + max_items;
     if (end > data_items.len) end = data_items.len;
     for (data_items[table_ctx.start..end], 0..) |data, idx| {
-        const row_bg =
-            if (table_ctx.active and table_ctx.start + idx == table_ctx.row) table_ctx.selected_bg else if (idx % 2 == 0) table_ctx.row_bg_1 else table_ctx.row_bg_2;
+        const row_bg = rowBG: {
+            if (table_ctx.active and table_ctx.start + idx == table_ctx.row)
+                break :rowBG table_ctx.active_bg;
+            if (table_ctx.sel_rows) |rows| {
+                if (mem.indexOfScalar(usize, rows, table_ctx.start + idx) != null) break :rowBG table_ctx.selected_bg;
+            }
+            if (idx % 2 == 0) break :rowBG table_ctx.row_bg_1;
+            break :rowBG table_ctx.row_bg_2;
+        };
 
         const row_win = table_win.initChild(
             0,