Version bump script

[peterwilsoncc]

Description of the Change

Introduces a version bump script to make doing so easier. The script does the following:

• bumps the version in the NPM config files: package(-lock)?.json
• bumps the stable tag in readme.txt
• bumps the version in the main plugin file
• bumps the version constant in the main class file
• Adds an empty changelog entry to CHANGELOG.md with the associated link.
• Adds an empty changelog entry to readme.txt
• Removes all but the last four changelog entries from readme.txt to ensure the file is below wordpress.org size limits

Closes #293

Use of AI

Model: GPT-5.3-Codex • 7.7

How to test the Change

1. Run bin/version-bump.sh patch
2. Ensure the version number is bumped by 0.0.1
3. Ensure the old version number no longer appears as the current version anywhere - it should be removed in most places except the change logs
4. Review the PHP changes to ensure there are no syntax errors.

Changelog Entry

Developer - Introduce version bump script.

Credits

Props @peterwilsoncc

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added Critical Flows, Test Cases, and/or End-to-End Tests to cover my change.
• All new and existing tests pass.