Persist panel visibility/position within session

[kendallroth]

Currently the panel does not persist its visibility or position, which causes it to reset whenever the main game UI is hidden (ie. reloading, escape menu, etc). The panel visibility and position should be persisted and loaded automatically when the mod mounts in the UI.

This probably should come along with a settings UI for resetting position/visibility (in case it disappears).

[kendallroth]

This is referring specifically to persisting visibility within a game session; for persisting visibility/position within a save game, see #7

[kendallroth]

Closed in #8