* Automate the Flask release
A Flask release will now be published alongside each main extension
release. The version of each Flask release will be the same as the
extension version except it will have the suffix `-flask.0`.
* Programmatically remove build prefix
The create GH release Bash script derives the Flask version from the
Flask build filename by removing the build prefix, leaving just the
version. Rather than hard-coding the prefix size to remove, it is now
calculated programmatically so that it is easier to read and update.
* Fix tag publishing
The tab publishing step used the wrong credentials, and didn't properly
identify the commit author. This has now been fixed.
The `.sh` file extension is now used for all Bash scripts. This ensures
the files are recognized as Bash scripts by the ShellCheck CI job, and
by editors/IDEs for improved syntax highlighting.
