Update social badges

[loan-mgt]

add letterboxd badges

[PyvesB]

Not sure about this one, I feel like we're somewhat deviating from the "status badge" definition here. Do we also want to include those big banners some GitHub users put on their profiles (example below). Where do we want to draw the line in the sand?

[loan-mgt]

Understandable, looks like it's the direction of the platform, but not the goal of the project