* Relicense layouts under CC0
Layout definitions are licensed differently from the rest of the
application source code to allow use in other projects related or
unrelated to Unexpected Keyboard.
Some layouts are not re-licensed and their original copyright continues
to apply. The copyright notice is added at the top of the files.
* Contributing: Mention layout licensing
This separates the layout definitions from the special layouts
(bottom_row, greekmath) and other unrelated files (method, settings).
This is also a more intuitive location for layouts and make the resource
directory easier to navigate.
Under the hood, layouts are copied back into
build/generated-resources/xml.
