Make links in stream descriptions clickable

[FeldrinH]

A common way to make important links always available is to add them to the stream description. This works great on desktop, but on mobile these links cannot be clicked and cannot be copied, making the links effectively inaccessible on mobile. This is very inconvenient and it would be nice if these links were clickable.

PS: Full markdown support as requested in https://github.com/zulip/zulip-mobile/issues/4944 would be ideal, but I think it is essential that links in stream descriptions at least be clickable, if implementing markdown support is too complicated.

[gnprice]

Thanks for the feedback! I agree this is something we should do.