Fix dev command for TS support

Gosh, I'm really down this rabbit hole, huh? :p Anyway, turns out the `vercel dev` command contains a _fork_ of ts-node that doesn't respect the `ts-node` override key in `tsconfig.json`. But it does respect the env var!

So I've now set up `yarn start` to invoke `vercel dev` with the new env, which in turn invokes `yarn dev` to start the create-react-app dev server. Whew! (Probably a better dev experience tbh.)

package.json

@@ -50,7 +50,8 @@
     "xmlrpc": "^1.3.2"
   },
   "scripts": {
-    "start": "yarn build-cached-data && REACT_APP_IMPRESS_LOG_IN_AS=$IMPRESS_LOG_IN_AS react-scripts start",
+    "start": "TS_NODE_COMPILER_OPTIONS='{\"target\": \"esnext\", \"module\": \"commonjs\"}' vercel dev",
+    "dev": "yarn build-cached-data && REACT_APP_IMPRESS_LOG_IN_AS=$IMPRESS_LOG_IN_AS react-scripts start",
     "build": "yarn build-cached-data && react-scripts build",
     "vercel-build": "yum install libuuid-devel libmount-devel && cp /lib64/{libuuid,libmount,libblkid}.so.1 node_modules/canvas/build/Release/",
     "test": "react-scripts test --env=jsdom",
@@ -82,6 +83,7 @@
     ]
   },
   "devDependencies": {
+    "5to6-codemod": "^1.8.0",
     "apollo-server-testing": "^2.12.0",
     "auth0": "^2.28.0",
     "dotenv-cli": "^3.1.0",
@@ -90,6 +92,7 @@
     "jest-image-snapshot": "^4.3.0",
     "prettier": "^2.0.5",
     "react-is": "^16.13.1",
-    "ts-node": "^9.1.1"
+    "ts-node": "^9.1.1",
+    "vercel": "^21.2.2"
   }
 }

tsconfig.json

@@ -1,6 +1,6 @@
 {
   "compilerOptions": {
-    "target": "es5",
+    "target": "esnext",
     "module": "esnext",
     "downlevelIteration": true,
     "strict": true,
@@ -23,6 +23,7 @@
   },
   "ts-node": {
     "compilerOptions": {
+      "target": "esnext",
       "module": "commonjs"
     }
   },