Add make-dist support and github workflow

[bandoti]

This change adds a new github workflow for generating a distribution tarball containing required sub-modules, fixing #6 .

In addition, it fixes some build issues with MSYS2 related to header files referenced as symbolic links.

[bandoti]

@cyanogilvie

The make-dist support is working now. Please note that I had to remove the symlink behavior which tcl-tomlcrypt uses in order to be able to support the tarballs on MSYS2, as Windows does not play nicely with symlinks. In particular:

• Delete Makefile.teabase.in

• Modify Makefile.in to use path relative to builddir:
  include $(top_builddir)/teabase/Makefile

• Modify configure.ac to add teabase include path and reference teabase/Makefile directly:

  TEA_ADD_INCLUDES([-I$srcdir/teabase])
  ...
  
  AC_CONFIG_FILES([Makefile pkgIndex.tcl teabase/Makefile])
  

Another thing to note is that the action permissions had to be adjusted, and the token set, to allow pushes to the release:

    permissions:
      contents: write

  token: ${{ secrets.GITHUB_TOKEN }}

If you are happy with this change, I would be happy to make the similar changes to tcl-tomlcrypt supporting MSYS2. Also note I have the CI run and generated test release here:
https://github.com/TclMonster/parse_args/actions/runs/11730151951
https://github.com/TclMonster/parse_args/releases/tag/v0.5.1