Deprecate puppeteer-firefox in transition to Firefox support in puppeteer

[mjzffr]

As of v2.1.0 puppeteer has alpha-level support of Firefox Nightly via the protocol described at https://wiki.mozilla.org/Remote.

Meanwhile, puppeteer-firefox and the "Juggler" fork of Firefox that it depends on are no longer maintained for some time.

• Add a deprecation message to the puppeteer-firefox package, but keep it available for the time being.
• Remove the code under /experimental
• Remove unit test runs against Juggler from CI (Wrong chromium version in v2.0.0 release notes (r706915 not r705776) #5136 )
• Add deprecation message to Juggler repo; archive it.

[mjzffr]

/cc @whimboo

[mjzffr]

@mathiasbynens Proposed deprecation warning to add to puppeteer-firefox package:

Firefox support is gradually transitioning to the puppeteer package. As of puppeteer v2.1.0 you can interact with Firefox Nightly. The puppeteer-firefox package will remain available until the transition is complete, but it is no longer actively maintained. For more information visit https://wiki.mozilla.org/Remote

[mjzffr]

@mathiasbynens What's left to do before the proposed deprecation warning is added?

[mathiasbynens]

I’ve added it: https://www.npmjs.com/package/puppeteer-firefox You also get this message when running npm install puppeteer-firefox.

[stale]

We're marking this issue as unconfirmed because it has not had recent activity and we weren't able to confirm it yet. It will be closed if no further activity occurs within the next 30 days.

[whimboo]

This work has been done by PR #8307.