feat: add script to output options prototype JSON

We now define the options via Typescript instead of a JSON file, but we
need the options prototype in JSON format so we can sync new features to
the kill switch server.

Thus, this CL adds a script which outputs this data, which can be used
with the syncfeatures binary. It also updates the docs on how to sync
the features.

Change-Id: I238e4521f00e4b5602712fa8d2b4360a1f7fb827
diff --git a/tsconfig.json b/tsconfig.json
index 3c671ac..363c4b1 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -8,5 +8,10 @@
     "target": "es2019",
     "moduleResolution": "bundler",
     "allowJs": true
+  },
+  "ts-node": {
+    "compilerOptions": {
+      "module": "commonjs"
+    }
   }
 }