[Monetization flow - Content] Tag listener

[dianafulga]

1. Setup MutationObserver to detect link tags
2. For each found tag check if the href has a valid JSON response (based on OP Spec)
3. For each valid tag save details (Wallet Address response - authServer, resourceServer etc ... + a unique identifier - uuidv4, w/e)
   in a map/array/something and send START_MONETIZATION (payload wallet JSON - opt requestId TBD) event to background script

We need to take iframes into consideration as well - only the first monetization link from the page (only the head element and only iframes that have monetization in the allow list)