Improve discoverability/awareness of the browser extension

[christinaforney]

The browser extension is extremely useful to users and we show them a notice when they first come to Sourcegraph to install it. This notice is introduced too early, and the user typically dismisses it because they are overwhelmed by the product.

Make sure that users know that the browser extension exists, and help them quickly configure it (auto-configure from a private instance?)

Make sure users know what is going on with the browser extension when they are viewing code on a code host.

Problem statements

• I don't know what to expect from the browser extension.
• I don't want to be annoyed with notices about the browser extension if my code host has a native integration.
• I want to know if the browser extension is working, and if it is expected to be working.

[AlicjaSuska]

RFC 221

[AlicjaSuska]

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