GitHub automatically generates .zip files of the repository contents. Moving the library to the root of the repository would allow that file to be used for installation, rather than requiring this complex deployment process. This will allow users to follow the same installation process as they would use for any other Arduino library hosted on GitHub, rather than a non-standard process.

This repository structure is also required if you want to add your library to the Arduino Library Manager index, which provides an even easier installation and update process for the users.

My proposed repository structure is:

NonBlockingRTTL (repository root)
|_library.properties
|_keywords.txt
|_examples
|_src
  |_NonBlockingRtttl.h
  |_NonBlockingRtttl.cpp

That is the Arduino Library Format 1.5. If you prefer the 1.0 format then the source files can be placed in the repository root instead of in the src subfolder.