Problem:
The generated ToC (table of contents) uses anchors derived from the
heading title, e.g. the "Global Plugins" heading yields:
https://neovim.io/doc/user/usr_05.html#_global-plugins-
so if the heading title changes, then the old URL (anchor) is broken.

Solution:
:help tags change less often than heading titles, so if a heading
contains a *tag*, use that as its anchor name instead. Example:
https://neovim.io/doc/user/usr_05.html#standard-plugin

- Improve generated HTML by updating parser which includes fixes for
  single "'" and single "|":
  https://github.com/neovim/tree-sitter-vimdoc/pull/31
- Updated parser also fixes the conceal issue for "help" highlight
  queries https://github.com/neovim/tree-sitter-vimdoc/issues/23 by
  NOT including whitespace in nodes.
  - But this means we need to restore the getws() function which scrapes
    leading whitespace from the original input (buffer).

- increase python line-length limit from 88 => 100.
- gen_help_html: fix bug in "tag" case (tbl_count => tbl_contains)

ref #15632
fix #18215
fix #18479
fix #20527
fix #20532

Co-authored-by: Ben Weedon <ben@weedon.email>

Problem:
- Docs HTML: "foo ~" headings (column_heading) are not aligned with
  their table columns/contents because the leading whitespace is not
  emitted.
- taglinks starting with hyphen like |-x| were not recognized.
- keycodes like `<foo>` and `CTRL-x` were not recognized.
- ToC is not scrollable.

Solution:
- Add ws() to the column_heading case.
- Update help parser to latest version
  - supports `keycode`
  - fixes for taglink, argument
- Update .toc CSS. https://github.com/neovim/neovim.github.io/issues/297

fix https://github.com/neovim/neovim.github.io/issues/297

Problem:
Since https://github.com/neovim/tree-sitter-vimdoc/commit/eba7b5b646546d9fed9b40b2c72b9cc0048f1dfa
any opening paren and its leading whitespace " (" are missing in the
generated HTML. Example:

    Use ":qa!<Enter>" (careful, all changes are lost!).
                     ^^missing
    Position the cursor on a tag (e.g. bars) and hit CTRL-].
                                ^^missing

Solution:
The main recursive loop only processes named children, so check
named_child_count() instead of child_count().  Then anonymous nodes
won't get lost.

- Docs HTML: improvements in https://github.com/neovim/tree-sitter-vimdoc
  allow us to many hacks in `gen_help_html.lua`.
- Docs HTML: support nested lists.
- Docs HTML: avoid extra newlines (too much whitespace) in old
  (preformatted) layout.
- Docs HTML: disable golden-grid for narrow viewport.
- Workaround for https://github.com/neovim/neovim/issues/20404

closes https://github.com/neovim/neovim/issues/20404

Generate correct leading whitespace for argument, taglink, tag, etc.

- adapt to parser changes from https://github.com/vigoux/tree-sitter-vimdoc/pull/16
- numerous other generator improvements