feat(treesitter): bundle :help parser and queries

parser from https://github.com/vigoux/tree-sitter-vimdoc
queries from nvim-treesitter

runtime/queries/help/highlights.scm

@@ -0,0 +1,14 @@
+(headline) @text.title
+(column_heading) @text.title
+(tag
+   "*" @conceal (#set! conceal "")
+   name: (_) @label)
+(option
+   name: (_) @text.literal)
+(hotlink
+   "|" @conceal (#set! conceal "")
+   destination: (_) @text.reference)
+(backtick
+   "`" @conceal (#set! conceal "")
+   content: (_) @string)
+(argument) @parameter