Create empty interfaces: "Decoder" and "Encoder".
Add "electron" into the depndencies of "example".
Create an empty interface: "Image".
Create classes related to GIF.
Add a class to store a raw image.
Classes imlementing "Image" should have "toByteArray" method.
"Encoder" and "Decoder" interfaces are needless.
"GifEncoder" encodes bitmap images to GIF with specified options.
Merge branch 'feature/design-interface' into prototype