DevHub social feed should reference to actual DevHub post instead of displaying full content

[petersalomonsen]

Is your feature request related to a problem? Please describe.

This was originally described in #137, but is split up into a separate issue here.

Original problem description is:

"DevHub cross-posts top-level posts under its own Social Feed, and comments and likes left there are not displayed on DevHub."

Describe the solution you'd like

In order to direct the user to reply/like the actual DebHub post, and not in the social feed, it's better if the social feed contains references to the DevHub posts, and not the full content. This will also save contract storage spent for the user. Also the social feed could then contain info about if there was a reply to a post, and then reflect that there is ongoing activity. I think this is more interesting information in the social feed rather than the full content. The social feed should be a place where you can see which ideas / solutions that has activity, and short posts there with title and link for both new posts and replies would reflect that in a better way.