Docs: Update JavaScript build and setup with wp-scripts updates

[mkaz]

Description

Closes #13712.

Updates the build and setup section of the JavaScript tutorial with the new simplified commands included in wp-scripts. Removes webpack and babel configs and replaces recommending to use the default configs using wp-scripts build|start

How has this been tested?

Follow the instructions, in the tutorial which includes a simple block you can create to test.
Until the wp-scripts gets published you will need to add a local reference to @wordpress/scripts package.

For me Gutenberg is one directory up from my sample plugin so my package.json entry looks like:

    "@wordpress/scripts": "file:../gutenberg/packages/scripts",

View documentation live on branch here

Depends on #14168

[youknowriad]

Nice ❤️

[chrisvanpatten]

Looks great! A few small suggestions…

[mkaz]

@nosolosw @gziolo In my testing, it was still required to install the following packages, they were not picked up as dependencies of @wordpress/scripts

webpack webpack-cli @wordpress/babel-preset-default babel-plugin-transform-react-jsx

The babel-plugin-transform-react-jsx looks to be the only one not specified in the scripts package.json. I'm not sure why the others didn't work for me, my hunch is because of the local package references.

Following the instructions in the docs and installing and it all works great, so much simpler!

[oandregal]

@mkaz for ESNext we need to land #14168 first. I'm waiting for Travis so I can merge :)

This example oandregal/understanding-gutenberg#7 shows how it works (I'm using JSX syntax and arrow functions in the src/index.js and the build/index.js is transpiled properly).

changes addressed; awesome stuff @mkaz!

[oandregal]

This is great to see! I pushed some commits, feel free to remove them if you don't like them. I thought it'd be faster to commit than to write the suggestion :)

I'm approving so it's ready to go, although I understand that we want to merge this after the packages' release.

[gziolo]

Awesome work. Thanks for putting this together and updating with the latest changes introduced. It should be very helpful moving forward. We probably should also reference this document from @wordpress/scripts readme file as well.

[gziolo]

Next step, hot module reloading support? :)