connector.yaml: validate Git tag and connector version

[hariso]

Part of ConduitIO/conduit#1523.

Making sure that a pushed tag is the same as specification.version from connector.yaml is part of Version Handling explained in ConduitIO/conduit#1522.

Feature description

4. Version handling

We need to add some safeguards to ensure the connector.version field in connector.yml contains the correct version and matches the git tag. The idea is to use two GitHub actions to automate this:

• A GitHub action is triggered BEFORE release, checks if the pushed tag matches the tag in connector.yml. If it does NOT match, it deletes the tag and fails the action, preventing the release.
  ...
  The result is a connector.yml that contains the correct latest released version which matches the last git tag.

[hariso]

Fixed by #60.