v0.6.7

ui: Redesign user interface

Introduces a new user interface that looks much nicer, is easier to
navigate with controllers, provides more context to users, and is
scalable. Some additional features are included.

* Adds 'popup menu' with actions that can be used easily from controller
* Adds 'main menu', unifying other configuration dialogs
* Adds port-forwarding user interface
* Adds screenshot feature
* Adds volume control feature
* Adds gamepad auto-bind option
* Adds vsync configuration option
* Adds auto UI scaling
* Adds preferred window size selection
* Adds AV pack selection
* Exposes some existing config items in GUI

v0.6.6

tomlplusplus: Update submodule

v0.6.5

.github: Make all release tags follow v<semver> convention

Replace xemu-v*, gh-release/* tagging with typical semver vX.Y.Z, which
plays nicer with GitHub releases. Increments patch version on push
to master.