Added a list to the ChannelManager class that tracks
which tabs I closed. Works like a stack, where it adds to the end
every time I close a tab. Then added a function that uses
this list to open the last closed channel, and added a shortcut inside of ChatOverlay,
similar to how jmeng implemented shortcuts.
Code is currently untested.
I tried also updating the colours to the "new" versions from designs but
they don't match due to colour profile differences (so I'm not yet sure
if they are correct or not) and also don't look great without all the UI
elements also being updated.