Set up automatic semver

[AlexStormwood]

• [ ] Use Github Actions to modify release semver when generating new packages nightly based on the following rules
• [ ] Increment MAJOR number when any commits tagged as MAJOR are detected
• [ ] Increment MINOR number when any commits tagged as MINOR are detected
• [ ] Increment PATCH number when any commits tagged as PATCH or without tag are detected

Remember to adhere to semver rules for this! Resources:

• https://semver.org/
• https://devhints.io/semver
• https://en.wikipedia.org/wiki/Software_versioning
• https://github.com/marketplace/actions/semver-release
• https://github.com/marketplace/actions/create-new-semantic-version

[AlexStormwood]

Created the Github Action script to update the Unity project's "bundleVersion" property, now this repository just needs a proper set of workflow files to use that action!

[AlexStormwood]

Created the Github Action script to update the Unity UPM package "version" property, now this repository just needs a proper set of workflows to use that action as per the checklist!