Added a new script to package the webextension. This will automatically
build and zip the source code and the webextension for upload. It take a
version as an argument and then checks the version in the manifest, and
locally commits a version bump.
Note that getMessage in the badge depends on having a complete set of
translations, unlike the webextension, which will fallback to the
default for a string.
Some files were omitted in the .eslintignore, left as an exercise to the
reader.
We probably want to reduce amount of globals overall and use proper es
modules.
