Build website from master branch www directory

This add the source files from website branch into the master branch under the www directory.

This change is a work-around for the issue documented in #56 (closed), but it also doesn't hurt to make the webpage source be in the master branch like Mesa.

Successful pipeline: https://gitlab.freedesktop.org/jljusten/waffle/pipelines/127480

Deployed webpage with 1.6.1: https://jljusten.pages.freedesktop.org/waffle/

Does the www directory seem ok? Or, should we use docs like Mesa?

Cc: @evelikov, @eric