Updated es-lint docs to instruct how to install eslint-config-react-app

[lukebrobbs]

Description

• Updated es-lint docs to recommend using eslint-config-react-app
• Removed extra documentation to make the instructions a little more focused.

Related Issues

#12980

[KyleAMathews]

Thanks for jumping on this!

[dakebl]

Might be worth mentioning and linking the shipped ESLint file here too for reference. So that developers are aware that a more complex version exists internally: https://github.com/gatsbyjs/gatsby/blob/master/.eslintrc.json

[KyleAMathews]

Tweaked the copy some to remove mentions of Prettier and to be more direct that Gatsby ships with .eslintrc and you add your own config file only if you want to modify that.

Thanks @lukebrobbs!

[gatsbot]

Holy buckets, @lukebrobbs — we just merged your PR to Gatsby! 💪💜

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Thanks again!

[JDDoesDev]

I know this issue has been closed for a while, and I can open a new one if need be, but I find the language confusing on https://www.gatsbyjs.org/docs/eslint/

In the main section it says:

You’ll replicate (mostly) the ESLint config Gatsby ships with so you can then add additional presets, plugins, and rules.

but further down the page it says:

When you include a custom .eslintrc file, Gatsby gives you full control over the ESLint configuration. This means that it will override the built-in eslint-loader and you need to enable any and all rules yourself.

On first read-through, it appears to contradict the first statement and imply that by using the snippet on the page, you're losing out on all the things from the default config.