Tags get generated to a .TAGS dotfile to then replace TAGS via hardlinks

[psprint]

Basically:

ctags … -f .TAGS
ln -f .TAGS TAGS
rm -f .TAGS

for lowest possible inconsistency time when regenerating index.

Also, pass -G option to universal-ctags, so that shell files without .zsh extension get recognized by file constents (hashbangs and vim/emacs modelines). Also fixed modeline in zi-browse-symbol because it wasn't recognized.

Motivation and Context

When an editor reloads the file when its timestamp changes it might read incomplete contents. The hardlink way should be best possible (however it probably does the same what mv -f .TAGS TAGS does, but it's good to be as much explicit as possible).

Related Issue(s)

Usage examples

# Establish auto make every 5 seconds with `zservices/make-server`
zinit lucid service'make' param'MSERV_CONF_DIRS→~/github/zinit;
         MSERV_CONF_INTERVAL→5;MSERV_ARGS→tags-emacs' \
            for zservices/make-server

To then browse tags with Ctrl-k (or Alt-Shift-q after #387).

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[psprint]

It's a documentation for the feature of browsing Ctags index and ln -f A B ; rm -f A robustness trick, safe to merge. It'l publish the extra feature of TAGS browser. Could it be merged, @vladdoster ?

[psprint]

Closed because overlaps #402,