Add main and source fields

Author: devongovett

packages/runtimes/rsc/package.json

@@ -13,6 +13,8 @@
     "type": "git",
     "url": "https://github.com/parcel-bundler/parcel.git"
   },
+  "main": "lib/RSCRuntime.js",
+  "source": "src/RSCRuntime.js",
   "exports": {
     ".": {
       "react-server": "./resources.js",