fix(build): vimdoc tags are not validated #32801

Problem:
"make lintdoc" is not validating vimdoc (:help) tags.

Solution:
- Call `lang_tree:parse()` to init the parser.
- Load netrw 🤢 explicitly, since it was moved to `pack/dist/opt/`.
- Fix invalid help tags.

runtime/lua/vim/_meta/options.lua

@@ -4640,7 +4640,7 @@ vim.go.pm = vim.go.patchmode
 --- ```
 --- - A directory name may end in a ':' or '/'.
 --- - Environment variables are expanded `:set_env`.
---- - When using `netrw.vim` URLs can be used.  For example, adding
+--- - When using `netrw` URLs can be used.  For example, adding
 ---   "https://www.vim.org" will make ":find index.html" work.
 --- - Search upwards and downwards in a directory tree using "*", "**" and
 ---   ";".  See `file-searching` for info and syntax.