why inject it inside the browser?
it can be message and event based, allowing multiple extensions. nip07 had the same issue of extensions fighting.
you emit an event or broadcast a message using the ...
so example.
extensions add an event listener to the page, listening the event "nip123:requestAPI" for example.
then the page loads and the webapp listens the event "nip123:announceAPI", then it dispatches the event "nip123:requestAPI".
then the extension listening on that event respond with their name, description, logo, and api object by dispatching the event "nip123:announceAPI".
then the app can pick one or show the users options to pick one. or multiple. etc.
extensions add an event listener to the page, listening the event "nip123:requestAPI" for example.
then the page loads and the webapp listens the event "nip123:announceAPI", then it dispatches the event "nip123:requestAPI".
then the extension listening on that event respond with their name, description, logo, and api object by dispatching the event "nip123:announceAPI".
then the app can pick one or show the users options to pick one. or multiple. etc.