Add flat by @netless-io (#1076)

contents.json

@@ -28698,6 +28698,21 @@
       "source": "https://github.com/ryanlintott/DefibHeart",
       "date_added": "Jun 12 2022",
       "suggested_by": "@dkhamsing"
+    },
+    {
+      "title": "Flat",
+      "category-ids": [
+        "communication",
+        "education"
+      ],
+      "tags": [
+        "swift"
+      ],
+      "screenshots": ["https://raw.githubusercontent.com/netless-io/flat-ios/main/art/flat-showcase.png"],
+      "license": "mit",
+      "source": "https://github.com/netless-io/flat-ios",
+      "date_added": "Jun 13 2022",
+      "suggested_by": "@vince-hz"
     }
   ]
 }