Ensure Firefox & Safari compatibility

[headquarter8302]

Ref:

• https://issues.chromium.org/issues/40556351
• https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Chrome_incompatibilities

The extension currently explicitly uses the chrome namespace to access the WebExtensions API. While the sub-namespaces and methods in there are agnostic to all major browsers (at least since Chrome MV3), using the standard browser namespace is much preferred to maximize compatibility.

The hope is that we can either:

1. Switch the namespace to browser entirely, or
2. Stub the browser namespace with either chrome or browser depending on the environment

Feedback and concerns are welcome