Problem:
Flow layout looks better on neovim.io. Nvim-owned help files should
switch to the new layout. Also lua-bit.txt doesn't use the same format
for function documentation as the other docs (such as api.txt).
Solution:
Switch to new layout. Tweak the function documentation to be in line
with the other docs style.
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.
