[Feature request] Random cached comic

[Arc676]

It would be nice if there were a way to pick a random comic but only among the cached ones for when you don't have an internet connection.

I might be able to work on this myself; could I have a hint as to which files are responsible for networking and random comic picking so I don't have to search through everything?

[mamaral]

I'm working (slowly) on a re-factor with some new features, that includes persisting comics for offline mode, so this falls under that feature I believe.