[Audio] Add GlobalMaxPooling1D layer

[zaleslaw]

We are missing some layers to support the export of models from Keras fully. One of them is the GlobalMaxPooling1D layer.

Add a layer class, write documentation for it, write a test for it, try, if possible, create a small trainable network with it (in your own GitHub) and attach a link here in the comments.

The layer should be placed here

As a reference implementation, the GlovalAvgPool2D layer could be used, but feel free to improve it!

If some refactoring to pooling layers could be applied, please, try to do it!

Also, support for export and import of layer in JSON format should be added (see ModelLoader.kt and ModelSaver.kt)

A detailed description of the layer can be found here

[mkaze]

I'll work on this.