Feature Request: Add library API

[RTK]

Hello,

for my use case I would like to use this package's functionality as library from my source code.

Right now most of this package's logic resides in the bin/tojunit.dart file. It would be more helpful to move the logic to the lib directory and have e.g., a CliRunner class that takes the arguments from the binary file. This would allow me to use the same logic as the binary includes right now.

For now I have to rebuild some functionalities (e.g. reading and then splitting per line my machine test output file) and also add additional dependencies such as "testreport", which is unnecessary since this package already contains this logic, but unfortunately inaccessible from source code.

Best regards!