Add GitHub Actions script for releases on 3.2

[krashish8]

Changes proposed in this pull request:

• Ports Add GitHub Actions script for releases on 3.1 #1857 to 3.2
• Fixed NEWS and release_notes (changed #1825 to #1850)

@pgRouting/admins

[krashish8]

The NEWS was not in proper markdown format, (e.g. bold should be ** ** not * *, hyperlinks should be [ ]( )). Therefore I modified the Perl script and removed the newline character in release_script, so that it is in proper markdown.

[cvvergara]

Actually with the Action you created to have automatically posted changes on the tag:
https://github.com/pgRouting/pgrouting/blob/develop/doc/src/release_notes.rst#pgrouting-320-release-notes

TODO:
Create an issue about increasing the version number for sphinx
Relate this PR to that new issue