Netlify function support (init. version)

This commit attempts to set up netlify function support, it has hello.js example.
One big issue is that the nelify functions are essentially only work on :9000, which is a different port (8000) then what gatsby run in develop mode. I need to fix this, not sure how atm.

gatsby-config.js

@@ -1,3 +1,5 @@
+var proxy = require("http-proxy-middleware")
+
 module.exports = {
   siteMetadata: {
     title: 'Gatsby + Netlify CMS Starter',
@@ -74,4 +76,17 @@ module.exports = {
     }, // must be after other CSS plugins
     'gatsby-plugin-netlify', // make sure to keep it last in the array
   ],
+  // for avoiding CORS while developing Netlify Functions locally
+  // read more: https://www.gatsbyjs.org/docs/api-proxy/#advanced-proxying
+  developMiddleware: app => {
+    app.use(
+      "/.netlify/functions/",
+      proxy({
+        target: "http://localhost:8000",
+        pathRewrite: {
+          "/.netlify/functions/": "",
+        },
+      })
+    )
+  },
 }

netlify.toml

@@ -1,6 +1,7 @@
 [build]
   publish = "public"
   command = "npm run build"
+  functions = "lambda"
 [build.environment]
   YARN_VERSION = "1.9.4"
   YARN_FLAGS = "--no-ignore-optional"

package.json

@@ -36,15 +36,22 @@
   "license": "MIT",
   "main": "n/a",
   "scripts": {
-    "start": "npm run develop",
     "clean": "rimraf .cache public",
-    "build": "npm run clean && gatsby build",
+    "start:app": "npm run develop",
+    "start:lambda": "netlify-lambda serve src/lambda",
+    "start": "run-p start:**",
+    "build:app": "npm run clean && gatsby build",
+    "build:lambda": "netlify-lambda build src/lambda",
+    "build": "run-p build:**",
     "develop": "npm run clean && gatsby develop",
     "serve": "gatsby serve",
     "format": "prettier --trailing-comma es5 --no-semi --single-quote --write \"{gatsby-*.js,src/**/*.js}\"",
     "test": "echo \"Error: no test specified\" && exit 1"
   },
   "devDependencies": {
+    "http-proxy-middleware": "^0.19.1",
+    "netlify-lambda": "^1.4.2",
+    "npm-run-all": "^4.1.5",
     "prettier": "^1.15.3",
     "rimraf": "^2.6.2"
   }

src/lambda/hello.js

@@ -0,0 +1,17 @@
+// For more info, check https://www.netlify.com/docs/functions/#javascript-lambda-functions
+export function handler(event, context, callback) {
+    console.log("queryStringParameters", event.queryStringParameters)
+    callback(null, {
+      // return null to show no errors
+      statusCode: 200, // http status code
+      body: JSON.stringify({
+        msg: "Hello, World! " + Math.round(Math.random() * 10),
+      }),
+    })
+  }
+
+  // Now you are ready to access this API from anywhere in your Gatsby app! For example, in any event handler or lifecycle method, insert:
+  // fetch("/.netlify/functions/hello")
+  //    .then(response => response.json())
+  //    .then(console.log)
+  // For more info see: https://www.gatsbyjs.org/blog/2018-12-17-turning-the-static-dynamic/#static-dynamic-is-a-spectrum