chore: update docs and specs

docs/examples/0.15.x/server-dart/examples/databases/get-attribute.md

@@ -0,0 +1,25 @@
+import 'package:dart_appwrite/dart_appwrite.dart';
+
+void main() { // Init SDK
+  Client client = Client();
+  Databases databases = Databases(client);
+
+  client
+    .setEndpoint('https://[HOSTNAME_OR_IP]/v1') // Your API Endpoint
+    .setProject('5df5acd0d48c2') // Your project ID
+    .setKey('919c2d18fb5d4...a2ae413da83346ad2') // Your secret API key
+  ;
+
+  Future result = databases.getAttribute(
+    databaseId: '[DATABASE_ID]',
+    collectionId: '[COLLECTION_ID]',
+    key: '',
+  );
+
+  result
+    .then((response) {
+      print(response);
+    }).catchError((error) {
+      print(error.response);
+  });
+}