Closes #53 with an initial implementation. Uses dark checkers. Checker size is settable in settings for now.
Closes #59
Preps for #52 by making box model collapsable, adds icon to maximize the preview
Preps for changes in #49 by making the inspector toggle an icon (goal is to then add an "enable move/resize icon" in the toolbar)
Closes #41 which runs and screenshots a dummy app with the inspector and will fail on warnings
Adds timing toggle so that they can be hidden even when timings are available. Right now it'll stay in a disabled state unless timings are available. Might want a third color to show timings are available vs. staying disabled?