feat: add (note) node for highlighted notes and warnings

Add support for highlighting common call-out terms in documentation,
like the legacy syntax's `helpNote`, `helpWarning`, `helpDeprecated`.

However, only the variants with a colon are supported, as these account
for 99% of use in Nvim documentation without the danger of false
positives (and to keep symbol count low).

To keep state count low, all these are parsed as a single `(note)` node
that captures can disambiguate using `#any-of?`.

corpus/taglink.txt

@@ -146,7 +146,7 @@ Note: ":autocmd" can...
       (line)))
   (block
     (line
-      (word)
+      (note)
       (word)
       (word))
     (line

corpus/text.txt

@@ -64,3 +64,47 @@ line
   (block
     (line
       (word))))
+
+================================================================================
+notes
+================================================================================
+NOTE: this is a note
+
+Note that this is not a note.
+
+This is DEPRECATED:
+
+This is not DEPRECATED.
+
+
+--------------------------------------------------------------------------------
+
+(help_file
+  (block
+    (line
+      (note)
+      (word)
+      (word)
+      (word)
+      (word)))
+  (block
+    (line
+      (word)
+      (word)
+      (word)
+      (word)
+      (word)
+      (word)
+      (word)))
+  (block
+    (line
+      (word)
+      (word)
+      (note)))
+  (block
+    (line
+      (word)
+      (word)
+      (word)
+      (word))))
+

grammar.js

@@ -54,6 +54,7 @@ module.exports = grammar({
         $.codespan,
         $.argument,
         $.keycode,
+        $.note,
       ),
 
     // Explicit special cases: these are plaintext, not errors.
@@ -84,6 +85,12 @@ module.exports = grammar({
       ',',
     ),
 
+    note: () => choice(
+      'Note:', 'NOTE:', 'Notes:',
+      'Warning:', 'WARNING:',
+      'Deprecated', 'DEPRECATED:'
+    ),
+
     keycode: () => choice(
       /<[-a-zA-Z0-9_]+>/,
       /<[SCMAD]-.>/,

queries/help/highlights.scm

@@ -23,3 +23,9 @@
 (argument) @parameter
 (keycode) @string.special
 (url) @text.uri
+((note) @text.note
+   (#any-of? @text.note "Note:" "NOTE:" "Notes:"))
+((note) @text.warning
+   (#any-of? @text.warning "Warning:" "WARNING:"))
+((note) @text.danger
+   (#any-of? @text.danger "Deprecated:" "DEPRECATED:"))