Add local model

[JRMeyer]

add a way to install a local model to the STT Model Manager from a checkpoint folder or from TFLite + Scorer files

currently, you have to go through the model zoo, or manually hack the json file + dir structure to add a local model

[benpicco]

What JSON file did you edit? As the model zoo is no longer available, adding a model manually from the old releases would be the only option to get this running.