chore: update README

README.md

···
 // include a previously defined block
 [% INCLUDE myshinyblock %]
 
+// set a variable
+[% SET myvar = "foo" %]
+
+// include a template based on a variable path (would expand to my/foo/template.html
+[% INCLUDE my/$myvar/template.html %] 
+
+// try/catch 
+[% TRY %]
+    [% INCLUDE my/$myvar/template.html %]
+[% CATCH %]
+    [% INCLUDE bog/standard/template.html %]
+[% END %]
+
+[% TRY %]
+    [% INCLUDE anundefinedblock %]
+[% CATCH %]
+    oops!
+[% END %]
+
+
 // define a block
 [% BLOCK myshinyblock %]
     [% entry.name %]