Add Basque model v0.1.7

[zuazo]

I have made some more improvements to the previously shared model and #25 :

1. Trained from scratch with CUDA 11.6 and Tensorflow 1.15.5.
2. Added Wikipedia corpus to the scorer.
3. Optimized alpha and beta hyperparameters (134 trials).
4. Trained on Common Voice 12.
5. Added EusCrawl corpus to improve the LM.

The new accuracy:

Test Corpus	WER	CER
Common Voice	12.00%	4.48%

The models can be downloaded from here: https://aholab.ehu.eus/~xzuazo/models/Basque%20STT%20v0.1.7/