Add options panel

[whimboo]

There are a couple of hard-coded values in the extension that warrants at least for now a preferences section within the Add-ons manager. Those are simple general values that should affect every open sidebar panel:

1. Interval that is used to fetch new process data. By default it is set to 5s, and should be configurable between 1s, 2s, and 5s. Maybe a custom value would make sense too.

2. Option to enable or disable the transfer of pages (windows) information. By default it should be enabled, but to save processing power it should be deselectable.

3. Option to enable or disable the transfer of threads information. By default it should be enabled, but to save processing power it should be deselectable.

[whimboo]

@AnsahMohammad sorry for not replying earlier to your PR that you created earlier this year. I'm not sure what happened but I was never informed about any update and now when I wanted to check, due to some other fixes I have to do for PerfChaser, I noticed that #88 does no longer exist. I've never seen GitHub PRs disappearing so maybe this is a bug on GitHub.

Now I wanted to check back with you if you would still have the time and interest to continue on your patch that you may still have locally laying around.