This PR adds support for running unit tests with Googletest.

• Adds a Github action that builds and links the object files and executes the unit tests for each pull request against the development branch
• The Readme is extended to document how to execute the unit tests manually
• A dedicated CmakeLists.txt to build the testfiles and to include Googletest
• Simple unit tests for the Transmitter class to demonstrate usage (auto generated by Copilot)