overlay: OBS control window via WebSocket API (#773)

## Link to GitHub Issue or related Pull Request, if one exists
n/a

## Description of change
Adds an overlay window widget for controlling OBS over WebSocket.

Add new lines to the FPS widget that shows recording / streaming timers.

Show notifications for major state changes (stream started/stopped,
recording started/paused/resumed/stopped)

## Testing

src/spice2x/games/io.cpp

@@ -474,6 +474,8 @@ namespace games {
         vkey_defaults.push_back(VK_F12);
         names.emplace_back("Toggle Camera Control");
         vkey_defaults.push_back(0xFF);
+        names.emplace_back("Toggle OBS Control");
+        vkey_defaults.push_back(0xFF);
         names.emplace_back("Player 1 PIN Macro");
         vkey_defaults.push_back(0xFF);
         names.emplace_back("Player 2 PIN Macro");

src/spice2x/games/io.h

@@ -23,6 +23,7 @@ namespace games {
             ToggleScreenResize,
             ToggleFps,
             ToggleCameraControl,
+            ToggleOBSControl,
             TriggerPinMacroP1,
             TriggerPinMacroP2,
             ScreenResize,