To check for an existing HelpComplete function, exists('*HelpComplete')
should be used, as exists('HelpComplete') still returns 0 after sourcing
the ftplugin.

closes: vim/vim#20073

https://github.com/vim/vim/commit/c23bfd7922dc20d83c96203d9f8840d0673245cf

closes: vim/vim#20024

https://github.com/vim/vim/commit/0ca1121d1f3db831bd84a8f25f95484a90467d87

Co-authored-by: Peter Cardenas <16930781+PeterCardenas@users.noreply.github.com>

Problem:
`K` in help files may fail in some noisy text. Example:

      (`fun(config: vim.lsp.ClientConfig): boolean`)
                            ^cursor

Solution:
- `:help!` (bang, no args) activates DWIM behavior: tries `<cWORD>`,
  then trims punctuation until a valid tag is found.
- Set `keywordprg=:help!` by default.
- Does not affect `CTRL-]`, that is still fully "tags" based.

Problem:  Vim's help file doesn't have any syntax for comments, but
          'comments' and 'commentstring' are still set in the help
          buffer.
Solution: Unset 'comments' and 'cms' in help buffer

closes: vim/vim#17889

https://github.com/vim/vim/commit/adfea9b4e68f39744fcb6ce7840e1c3c3b4637db

Problem:

- Help tags provide a good way to navigate the Vim documentation, but
  many help documents don't use them effectively. I think one of the
  reasons is that help writers have to look up help tags manually with
  `:help` command, which is not very convenient.
- 'iskeyword' is only set for help buffers opened by `:help` command.
  That means if I'm editing a help file, I cannot jump to tag in same
  file using `Ctrl-]` unless I manually set it, which is annoying.

Solution:

- Add omni completion for Vim help tags.
- Set 'iskeyword' for `ft-help`

closes: vim/vim#17073

https://github.com/vim/vim/commit/0b540c6f381c63c2d80cc0aaef76b0df008b9f86

Co-authored-by: Christian Brabandt <cb@256bit.org>

Problem: Creating the table of contents for `gO` is complicated.

Solution: Use treesitter instead.

Help outlines, invoked by `gO`, displays the help section titles in the
location list window. This feature is implemented by setting the buffer
lines after opening the window, but this implementation breaks the
assumption that the quickfix window texts are consistently constructed
by the quickfix list items. I think we can use the conceal feature here.
Using conceal here improves interoperability between quickfix plugins,
and also simplifies the outline implementation.

Originally reported at https://github.com/itchyny/vim-qfedit/issues/12

Update runtime files
https://github.com/vim/vim/commit/4c05fa08c9739e307ddc88ac91ba6d208f1fd68e

Runtime file updates.

https://github.com/vim/vim/commit/214641f77df6f318a4b3a0b09723c19859a103f4

N/A:
vim-patch:26a280c47a1c