Clarify how Chrome extension permissions work

Article URL: https://web.hypothes.is/help/how-does-hypothesis-use-permissions-in-the-chrome-extension/

User feedback: This is an area of concern and your FAQ response does not clearly address my concern. My concern: Once I install your extension, will you do your thing: "we can inject the annotator code into the page, allowing you to add and read annotations", and "to maintain the state of the Hypothesis extension on windows or tabs you have open. We also need this in order to tell you (via the extension badge) when a page you visit has been annotated.", ON every tab that I open, whether I annotate that page or not? If you do, this is a concern as it will expose my browse history to your end, and data as well. Ideally, I would like your extension to kick in ONLY when I click on the extension icon, at which point, you enable that page / tab for annotation. Make me feel comfortable that you are restricted to ONLY that tab, with a change in color of the border for that tab, or have your icon appear only on that page, or change its color!

Review the linked Chrome extension permissions article and the FAQ response described in the issue. Start by comparing the documented permission behavior with the user's concerns about all tabs, browsing history, and activation. Done means the article clearly explains the scope of access and when annotation becomes active.

Written by the indexing model from the issue text.