Detect Firefox release channels

[filips123]

Add support to detect Firefox release channels (stable, beta, nightly), like for Chrome.

You would need to have a list of Firefox versions and their stability. You can get them from The Product-Details JSON API.

When parsing user-agent, you would need to check that list. If the version is stable, it should use "Stable" channel. If the version is beta, it should use "Beta" channel. If the version is not on the list, it should use "Nightly" channel.

And, if possible, also detect Firefox ESR version.