fix(docs-html): update parser

- 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).

runtime/lua/vim/shared.lua

@@ -100,10 +100,10 @@ end
 ---
 --- Examples:
 --- <pre>
----  split(":aa::b:", ":")     --> {'','aa','','b',''}
----  split("axaby", "ab?")     --> {'','x','y'}
----  split("x*yz*o", "*", {plain=true})  --> {'x','yz','o'}
----  split("|x|y|z|", "|", {trimempty=true}) --> {'x', 'y', 'z'}
+---  split(":aa::b:", ":")     => {'','aa','','b',''}
+---  split("axaby", "ab?")     => {'','x','y'}
+---  split("x*yz*o", "*", {plain=true})  => {'x','yz','o'}
+---  split("|x|y|z|", "|", {trimempty=true}) => {'x', 'y', 'z'}
 --- </pre>
 ---
 ---@see |vim.gsplit()|