add helper util to generate hashtag region keys

src/connection/connection.js

@@ -1769,6 +1769,13 @@ class Connection extends EventEmitter {
         });
     }
 
+    /**
+     * Set the flood scope to use by provided a 16-byte transport key.
+     * Passing an empty list will clear the scope.
+     * You can use `const transportKey = await TransportKeyUtil.getHashtagRegionKey("#region");` to easily generate keys
+     * @param transportKey Uint8Array 16-byte transport key, can be derived from first 16 bytes of sha256("#region")
+     * @returns {Promise<unknown>}
+     */
     setFloodScope(transportKey) {
         return new Promise(async (resolve, reject) => {
             try {

src/transport_key_util.js

@@ -0,0 +1,19 @@
+class TransportKeyUtil {
+
+    static async getHashtagRegionKey(regionName) {
+
+        // public hashtag regions must start with #
+        if(!regionName.startsWith("#")){
+            regionName = `#${regionName}`;
+        }
+
+        // Hash the message using SHA-256
+        const bytes = new TextEncoder().encode(regionName);
+        const hash = await crypto.subtle.digest("SHA-256", bytes);
+        return new Uint8Array(hash);
+
+    }
+
+}
+
+export default TransportKeyUtil;