docs: add new fs2 license info to top-level license

Author: roedoejet

LICENSE

@@ -105,6 +105,38 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 
+For everyvoice/model/feature_prediction/FastSpeech2_lightning/fs2/gst/attn.py:
+
+Copyright (c) 2019, Shigeki Karita.  All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+For everyvoice/model/feature_prediction/FastSpeech2_lightning/fs2/gst/model.py (sourced from ESPNet2):
+
+Copyright (c) 2020, Nagoya University (Tomoki Hayashi).  All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
 
 For files in everyvoice/model/aligner/DeepForcedAligner: