Improve OSS plugin template

Summary:
Based https://github.com/facebook/flipper/issues/1866 and running `npx flipper-plugin init` locally. Doesn't address the original issue

Fixes #1866

Reviewed By: passy

Differential Revision: D26147089

fbshipit-source-id: 608dc92c5ccc741b6e760ea5a5034f9444e951b7

desktop/pkg/templates/plugin/package.json.template

@@ -16,7 +16,7 @@
     "prepack": "flipper-pkg lint && flipper-pkg bundle",
     "build": "flipper-pkg bundle",
     "watch": "flipper-pkg bundle --watch",
-    "test": "jest"
+    "test": "jest --no-watchman"
   },
   "peerDependencies": {
     "flipper": "latest",
@@ -26,6 +26,7 @@
   "devDependencies": {
     "@babel/preset-react": "latest",
     "@babel/preset-typescript": "latest",
+    "@testing-library/react": "latest",
     "@types/jest": "latest",
     "@types/react": "latest",
     "@types/react-dom": "latest",
@@ -33,6 +34,7 @@
     "flipper": "latest",
     "flipper-plugin": "latest",
     "flipper-pkg": "latest",
-    "jest": "latest"
+    "jest": "latest",
+    "typescript": "latest"
   }
 }