Create version bump script

[peterwilsoncc]

Is your enhancement related to a problem? Please describe.

Create a version bump script based on https://github.com/10up/simple-podcasting

1. Update version in package, composer and plugin files
2. Replace instructions in release docs to use use said script for a version bump.

Designs

N/A

Describe alternatives you've considered

N/A

Code of Conduct

• I agree to follow this project's Code of Conduct