Add extraData example

src/PartyContext.tsx

@@ -36,6 +36,8 @@ export type APIEndPoint = { partyName: string, token: string };
 
 // Adapt this type to your desires
 export type SelfStatusExtraData = {
+  /* Example type: */
+  /* plusone: string; */
 };
 
 export const PartyContextProvider: React.FC<{ children: React.ReactNode }> = (props) => {

src/PartyPage.tsx

@@ -26,5 +26,27 @@ export const PartyPage: React.FC = () => {
                 </button>
             </div>
         </p>
+        {/*
+            Example usage of extraData:
+        <div>
+            <button onClick={() => {
+              const lastNum = parseInt(selfStatus.extra?.["plusone"] ?? "NaN");
+              if (isNaN(lastNum) || lastNum <= 0) return;
+              update({extra:{plusone: "" + (lastNum - 1)}});
+            }}>
+              -1
+            </button>
+            <button onClick={() => update({extra:{plusone: "1"}})}>
+              Du bringst {selfStatus.extra?.["plusone"] ?? "undefined"} Plus-Eins
+            </button>
+            <button onClick={() => {
+              const lastNum = parseInt(selfStatus.extra?.["plusone"] ?? "NaN");
+              if (isNaN(lastNum)) return;
+              update({extra:{plusone: "" + (lastNum + 1)}});
+            }}>
+              +1
+            </button>
+        </div>
+        */}
     </div>
 };