docs(help): specify h4 "function signature" format #42434master

Work towards enabling ["flow" layout](https://github.com/neovim/neovim/blob/9244da12e400ec0291450a5e9400d995e7a29b83/src/gen/gen_help_html.lua#L86-L88)
in all `:help` files.

Problem:
The final boss of vimdoc pseudo-structure: Vim's quasi-headings on
function signatures and excmd docs is visually distinctive but too
inconsistent for a nice parse rule.

Solution:
- Define the quasi-heading format as an "h4" variant, specified at
  `:help help-tag-heading`.
  - For simplicity and predictability, it is defined as any line that
    ends with a help tag(s) preceded by 2 or more spaces (or 1 tab).
- Update existing docs.
  - This one-time update has a lot of changes, but is very unlikely to
    conflict with ported Vim-patches because (1) Vim rarely adds new
    *excmds* that we want, and (2) *function* docs are auto-generated.

ref https://github.com/neovim/tree-sitter-vimdoc/issues/110

1 files changed, 1 insertions, 2 deletions

diff --git a/runtime/doc/sign.txt b/runtime/doc/sign.txt
index a3ca3bcf38..ed6c19687d 100644
--- a/runtime/doc/sign.txt
+++ b/runtime/doc/sign.txt
@@ -210,8 +210,7 @@ See |sign_place()| for the equivalent Vim script function.
 			:sign place 10 line=99 name=sign3
 			:sign place 10 line=99 name=sign3 buffer=3
 <
-							*E885*
-:sig[n] place {id} name={name} file={fname}
+:sig[n] place {id} name={name} file={fname}		*E885*
 		Change the placed sign {id} in file {fname} to use the defined
 		sign {name}.  See remark above about {fname} |:sign-fname|.
 		This can be used to change the displayed sign without moving