chore: move release process to a GitHub Actions workflow

[ctreatma]

This closes #109 by setting up a push-button GitHub Actions workflow that releases the SDK. The new workflow:

1. Inspects the commit log since the last GitHub release for Conventional Commit tags to determine the next release version
2. Updates the version file with the next release version and regenerates the SDK
3. Creates a GitHub release for the next release version
4. Builds the SDK JARs and publishes them to the packages page for this repo

[displague]

Does the new CI need to update the version file via a git commit? (the file is added in this PR so I'm wondering if it will become stale, or require manual updates from 0.7.0).

[displague]

We should also add a block to README.md on how to cut releases (or how robots do it)

[ctreatma]

@displague README has been updated with a Release section that links to the GitHub Actions workflow and documents the steps that the workflow executes

[github-actions]

This PR is included in version 0.8.0 🎉