refactor: roll handover (#451)

* style: tweak active colour

* refactor: create shared playback validation

* feat: allow handover from and to roll

packages/utils/src/validate-action/validatePlayback.ts

@@ -0,0 +1,10 @@
+import { Playback } from 'ontime-types';
+
+export function validatePlayback(currentPlayback: Playback) {
+  return {
+    start: currentPlayback !== Playback.Stop,
+    pause: currentPlayback === Playback.Play || currentPlayback === Playback.Roll,
+    roll: true,
+    stop: currentPlayback !== Playback.Stop,
+  };
+}