Start sample with HTTPS

WebRTC features are gated behind having a secure origin, but localhost
gets a pass. If trying to access the sample from a URL that doesn't look
like localhost, HTTPS is required.

README.md

@@ -12,4 +12,5 @@ You can retrieve your API key by visiting [https://accounts.simplewebrtc.com](ht
 2. Edit `src/index.tsx` as described above.
 3. `npm start`
 4. Go to [https://localhost:3000/](https://localhost:3000)
+5. The sample uses a self-signed cert that you will need to accept.
 

package.json

@@ -29,7 +29,7 @@
     "typescript": "^3.3.3333"
   },
   "scripts": {
-    "start": "react-scripts start",
+    "start": "HTTPS=true react-scripts start",
     "build": "react-scripts build",
     "test": "react-scripts test",
     "eject": "react-scripts eject",