add ticket purchase page

Co-authored-by: Jan-Marlon Leibl <jleibl@proton.me>
Reviewed-on: http://git.simonis.lol/projects/abiball/pulls/13
Reviewed-by: jank1619 <jan@kjan.email>

assets/controllers.json

@@ -0,0 +1,15 @@
+{
+  "controllers": {
+    "@symfony/ux-turbo": {
+      "turbo-core": {
+        "enabled": true,
+        "fetch": "eager"
+      },
+      "mercure-turbo-stream": {
+        "enabled": false,
+        "fetch": "eager"
+      }
+    }
+  },
+  "entrypoints": []
+}