Indication that the extension is alive

[eranshmil]

This feature is necessary to make sure that the plugin is alive, because most of the time we won't see a detected bot frequently.
So we will mark team members for themselves (the data will be saved in the server).
For example, if I'm a team member and I installed the extension, my own tweets will be marked with some new background.

• Add a new method to the ApiService that returns a mock team data.
• Mark all the team members tweets with a new background.
• Mark also in the profile page. (Add the background to the header image)