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/package.json b/package.json
index 162e67a..bcfe8a9 100644
--- a/package.json
+++ b/package.json
@@ -40,6 +40,7 @@
     "sass-loader": "14.2.1",
     "style-loader": "4.0.0",
     "ts-loader": "^9.5.1",
+    "ts-node": "^10.9.2",
     "typescript": "^5.4.5",
     "webpack": "5.91.0",
     "webpack-cli": "5.1.4",