* feat: add discussions tab
Adds code to load the discussions MFE in an iframe in the tab so the user isn't redirected to the LMS.
Adds code for the discussions tab, making it dynamically resize based on contents using a postMessage API.
* feat: update path based on user navigation inside discussions MFE
The discussions MFE will send path change events via the postMessage API so that the learning MFE path can be kept in sync. This will allow reloading a page without having the iframe revert to same path each time.
