Adopt feedbacks from upstream

example/official.kdl

@@ -30,3 +30,9 @@ package {
     }
   }
 }
+
+// https://github.com/zyedidia/micro/pull/3549
+examples-micro-3549 {
+  // https://github.com/zyedidia/micro/pull/3549#discussion_r1858298053
+  node-null null
+}

kdl.yaml

@@ -1,7 +1,7 @@
 filetype: 'kdl'
 
 detect:
-  filename: "\\.kdl"
+  filename: "\\.kdl$"
 
 rules:
   # Punctuation
@@ -40,25 +40,17 @@ rules:
   # Float
   - constant.number: '[-+]?(\d+)\.\d*'
   # Boolean and inf, nan without sign
+  # `\s` might be better than `\b` for separators? `foo-contantish` pattern is available for KDL node
   - constant.bool.true: '\btrue\b'
   - constant.bool.false: '\bfalse\b'
+  - constant: '\bnull\b'
   # Comments
   - comment:
       start: '//'
       end: '$'
       rules:
         - todo: '(TODO|FIXME|XXX|NOTE)'
-  # Slashdash comments
+  # Unavailable to support Slashdash comments
   # https://github.com/kdl-org/kdl/blob/de1dbd2c330c9193b836499db241787484627c3b/SPEC.md#L77-L79
   # vscode extension realizes this with lookahead and lookbehind, the regex feature cannot be used in micro
-  # https://github.com/kdl-org/vscode-kdl/blob/646d7b819d72b2f0d9dd05102a305506bafa3cf6/syntaxes/kdl.tmLanguage.json#L182-L199
-  # https://github.com/zyedidia/micro/issues/901#issuecomment-354931928
-  # So simplified it, it means this is inaccurate
-  - comment.block:
-      start: '^\s*/-'
-      end: '\s'
-      rules: []
-  - comment.block:
-      start: '/-{'
-      end: '}'
-      rules: []
+  # It is hard to support much of the use-case, so omitted. See https://github.com/zyedidia/micro/pull/3549#discussion_r1858265630