Allow sorting/reordering of channels in the channel list.

[travis79]

Is your suggestion related to a problem? Please describe.
I have a few rooms/channels that are closely named that I follow, and it sometimes means I have to be deliberate about which one I post in.

Describe the solution you'd like
If I could reorder the channels to some meaningful order, and not just the order that they were favorited in, etc. it would be very useful to me.

Describe alternatives you've considered
The only other way I've found to order my list, is to remove the channels and add them in the order I want. If I add a new channel, I basically had to start over and remove all my channels to add the new one in the order I wanted.

Additional context
N/A

[t3chguy]

Related #8614

[turt2live]

This is largely asking for a tagging implementation and/or manual ordering, which is covered by element-hq/element-meta#1558