Added getting started modal to home screen

src/docs/howTo/gettingStarted.md

@@ -0,0 +1,11 @@
+1. Start a game to generate a unique URL that can connect you and
+   your players.
+
+   Each game is recycled after 24 hours so make sure you create a new game when you play your next session.
+
+2. Invite players with your unique URL from step 1.
+3. Share a map, roll dice or share audio with your players.
+
+   All data is saved automatically to your computer so next session simply use the same browser and all your maps and tokens will be ready to go.
+
+That's it, no accounts, no paywalls, no ads, just a virtual tabletop.