React-devtools: Test Firefox multiprocess/e10s compatibility

[ngyikp]

Seems to work fine on my Firefox 51 nightly with multiprocess enabled, just need to add "multiprocess": true to the package.json after more confirmation.

[jnachtigall]

Works for me with Firefox Developer Edition 50 which is e10s enabled. So I agree that the manifest should be updated to report the addon as compatible so that it does not block the e10s rollout:

• https://blog.mozilla.org/addons/2016/08/02/multi-process-firefox-and-add-ons-a-call-to-action/
• https://developer.mozilla.org/en-US/Add-ons/Install_Manifests#multiprocessCompatible

[jlandersen]

Firefox 50 was just released where e10s is enabled if all addons have the manifest property - would be nice to have this in :-)