Hello!
I was looking at the [`with-firebase-hosting`](/zeit/next.js/tree/canary/examples/with-firebase-hosting) example and was having some various issues running it:
* `npm run serve` will choke on windows because trying to set enviroment variables with `NODE_ENV=production`
* `npm run build-funcs` failing because of babeljs mismatches between `@babel/cli@^7.0.0-rc.1` and `next@^6.0.3`
* Not being able to deploy because `firebase-tools` being a deprecated version.
I remedied this and also improved some other factors:
* Use standard JSON formatting on `package.json` so that `npm install` doesn't cause changes on every run. (a83e930)
* Remove "prettier" as a devDependency as there is no use of it in the example and most other examples does not have it as a dependency. (6095663)
* Update all dependencies. The simple usecase in this example didn't really require any changes to the code. (ccde086)
* [`firebase-admin@6`](https://github.com/firebase/firebase-admin-node/releases/tag/v6.0.0)
* [`firebase-functions@2`](https://github.com/firebase/firebase-functions/releases/tag/v2.0.0)
* [`firebase-tools@4`](https://github.com/firebase/firebase-tools/releases/tag/v4.0.0)
* [`firebase-tools@5`](https://github.com/firebase/firebase-tools/releases/tag/v5.0.0)
* [`firebase-tools@6`](https://github.com/firebase/firebase-tools/releases/tag/v6.0.0)
* Make `npm run serve` runnable on windows using [`cross-env`](https://www.npmjs.com/package/cross-env). (b20dda7)
* Update `.gitignore` to ignore firebase cache (bf761b7)
* Remove `src/app/.babelrc` that seems to have been added as a previous bugfix but doesn't seem to do anything currently. (1b02045)
* Remove point from [`README.md`](https://github.com/zeit/next.js/blob/canary/examples/with-firebase-hosting/README.md) that was mentioning any `predeploy` hooks in `firebase.json` as they were removed in 4f4b7a1bce. (5636d9f)
* Use the possibility added by upgrading `firebase-tools` to [`>=4.0.0`](https://github.com/firebase/firebase-tools/releases/tag/v4.0.0) and `firebase-functions` to [`>=2.0.0`](https://github.com/firebase/firebase-functions/releases/tag/v2.0.0) to make the deployable functions use node 8 rather than node 6. Also make babel compile with node 8 as target for less polyfills etc. (c954cc2)
* Added comment to [`README.md`](https://github.com/zeit/next.js/blob/canary/examples/with-firebase-hosting/README.md) explaining how firebase deploys to node 8 and that babel will compile code for node 8. (d8b2e65, 91953dc)
This was tested to `serve` on windows, linux(WSL) and on mac. Deploy was tested on linux(WSL) and mac.
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This PR is a based on #5806 with correct base.
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🔔 @jthegedus @timneutkens
* Next.js v5 update, _error & _document bugs fixes
* document clean script
* remove old build artefact
* add babelrc
* reset next.js version to 'latest' from '^5.0.0'
* typo in readme
* format code
* remove _files as they were a fix for a solved, but unreleased problem
