Update selection foreground/background to be reverse foreground/background, and add theming for tabs and windows

[manvithn]

Currently selection seems to use the default values in the kitty reference. This PR updates those to reverse foreground and background colors, which seems to be the intention in the hyper-snazzy theme (transparency is used because hyper terminal doesn't actually support setting foreground color). Also add theming for tabs and windows (splits).