Allow multiple Pontoon instances

[yarons]

User

I'm a translator using several different Pontoon instances, currently I can only use the add-on with one of them.

Feature description

Support multiple instances so that I can see stats from Mozilla and additional instances (Zabbix recently migrated to Pontoon).

[MikkCZ]

Hi @yarons .

Thank you for submitting the feature request. How would you rate the following options in terms how close they are the the best workflow possible:

• install the add-ons multiple times, one for each Pontoon instance
• single add-on showing information and notifications from all Pontoon instances simultaneously
• show information and notifications from a single Pontoon instance (like now) with an easy option to change the instance on-demand

[yarons]

I believe the second is the most appealing, thank you.