Netlify-cms: Add a style guide to documentation contributor info

[cory-wc]

Is your feature request related to a problem? Please describe.
The Contributor Guides do not reference a style guide for the documentation. I'm not certain how to appropriately document things without creating major style/voice inconsistencies.

Describe the solution you'd like
Create a style guide that's available through the documentation Contributor Guide, or determine one that can be replicated.

Describe alternatives you've considered

Additional context
I found the style guide for the Kubernetes docs useful: https://kubernetes.io/docs/contribute/style/style-guide/#use-bold-for-user-interface-elements.

Related issues
Issue 1038

[kurtgcollins]

I'd be interested in contributing to this. Do we want to just reference a larger, more well known style guide with some exceptions?

[verythorough]

Nice suggestion for using the Kubernetes guide, @cory-wc

I think the only rule I don't _really_ like in it is Use normal style for string and integer field values, but even then I don't really see it as worth making an exception for.

I think linking to Kubernetes's style guide from the contributor guide would be a great start. What do you think, @kurtgcollins?

[kurtgcollins]

@verythorough - I agree that the Kubernetes guide looks pretty good. I think we could add a few more things for readability's sake, such as sentence length, but the Kubernetes guide is a great start.

[erquhart]

I'd only add that the Kubernetes guide feels like _a lot_ - we should try to make ours feel less so.

[MimiDumpling]

Hello! I'll start a Markdown file and make a PR to get this started. 😸

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.