Move local development openSCAD url to env vars

I think this make it easier to swap between using the aws endpoint and
local endpoint but without having to worry about accidentally committing
the local endpoint if you absent mindedly staging everything, and it
still defaults to aws so it's easy setup for anyone doing a fresh clone.

add OPENSCAD_BASE_URL="http://localhost:8080" to you .env file.

You will have to restart yarn rw dev for the url to swap over though.

Resolves #242

web/src/helpers/cadPackages/openScadController.js

@@ -1,5 +1,5 @@
-// const openScadBaseURL = 'http://localhost:8080' // for local development
-const openScadBaseURL =
+let openScadBaseURL =
+  process.env.OPENSCAD_BASE_URL ||
   'https://x2wvhihk56.execute-api.us-east-1.amazonaws.com/dev'
 
 export const render = async ({ code, settings }) => {