Linting to help contribution

[leptest]

Suggestion:
Adopt popular community configs and common linting tasks.

Why:
To help others when contributing to and integrating this project.

How:
Use eslint, prettier, stylelint, and/or an editorconfig.
Most of these have a popular community config that could be adopted.

• eslint: airbnb or standard are great.
• prettier: default with the options from package.json seems reasonable.
• stylelint: stylelint-config-standard looks good.

Info:
Related: #67 #68
Semi related: #71 #74 #73
(the semi related ones would have been caught/fixed by using a standard config)

You mentioned in #57 about certain things being removed when a developer forks the project, and i agree this would fall in that category. But i think they are important when contributing to this project.

What are your thoughts?

[ekoeryanto]

One more reason, developer who knows more than 1 programing language or framework use IDE as a (super hero) helper of remembering the API. I do, the same, and I hate that when I see zigzag red lines below the texts when I am writing 🔢

[leptest]

We could also just use the same configs as https://github.com/netlify/netlify-cms or https://github.com/gatsbyjs/gatsby?