Option to hide interaction bars

[ShadowJonathan]

Users seem to find the bottom bar annoying; https://beehaw.org/post/505992

[buresdv]

Reading the linked post, the user doesn't want a dedicated button for replying, but they want the bottom tab bar and top toolbar to be hidden upon scrolling

[ShadowJonathan]

Yes, but I also interpreted this feature request from that XY, but that's fair then

Also as a companion to mlemgroup/mlem#133

[EricBAndrews]

Renamed to "option to hide bars," this should be part of our post-launch cutomization update

[Sjmarf]

Duplicate of #38