docs: add package READMEs

packages/cli/README.md

···
+# @morkdeck/cli
+
+The main interface for using morkdeck. Contains commands:
+
+- `dev`, for previewing your presentation as you work on it
+- `build`, for building your presentation to an HTML output

packages/cli/deno.json

···
   "version": "0.0.0",
   "exports": "./main.ts",
   "imports": {
-    "@cliffy/command": "jsr:@cliffy/command@1.0.0-rc.8",
+    "@cliffy/command": "jsr:@cliffy/command@1.0.0-rc.8"
   }
 }

packages/core/README.md

···
+# @morkdeck/core
+
+Rendering engine for morkdeck, which converts a Markdoc file into an HTML
+string.

packages/runtime/README.md

···
+# @morkdeck/runtime
+
+State management for morkdeck during runtime.

packages/runtime/deno.json

···
 {
   "name": "@morkdeck/runtime",
   "version": "0.0.0",
-  "exports": "./mod.ts",
+  "exports": "./mod.ts"
 }

packages/server/README.md

···
+# @morkdeck/server
+
+Development server with live-reload capabilities, file watching, and esbuild
+integration for runtime bundling.

packages/server/deno.json

···
     "@std/async": "jsr:@std/async@^1.0.14",
     "@std/http": "jsr:@std/http@^1.0.20",
     "@std/path": "jsr:@std/path@^1.1.1",
-    "esbuild": "npm:esbuild@^0.25.9",
+    "esbuild": "npm:esbuild@^0.25.9"
   }
 }

packages/wc/README.md

···
+# @morkdeck/wc
+
+Lit-based Web Components that provide the core frontend functionality for
+morkdeck. Compiled and bundled with your presentation.

packages/wc/deno.json

···
     "@es-toolkit/es-toolkit": "jsr:@es-toolkit/es-toolkit@^1.39.9",
     "lit": "npm:lit@^3.3.1",
     "@lit/context": "npm:@lit/context@^1.1.6",
-    "motion": "npm:motion@^12.23.12",
+    "motion": "npm:motion@^12.23.12"
   }
 }