Mergeback

A simple github action to merge back master to a development branch.  This action uses an optional environment variable:

• BASE_BRANCH The base branch where master changes should be merged to. Defaults to develop.
• DESC_PATH The path in your repository for the PR body template. Defaults to .github/merge-instructions.md. If this file exists, this will be used for the description of the PR (only if it's not mergable). Environment variables can be used in this file, they will be resolved.

The action uses GitHub's REST API to create a PR and merge it remotely on GitHub's servers.