Add a Requirements & Installation doc

[verythorough]

As we break out the contents of the overworked Quick start doc, we should add a page about Requirements and Installation. Here's the rough outline, pulled from #598:

• Installation & requirements
  • content
    • must be stored in GitHub repo (for now)
    • supported content file types
  • ‘installing’ the app
    • /admin folder (can be hosted separate from content)
    • index.html: include CMS via <script> tag or npm
    • config.yml: explain purpose & location, link to full reference

We may want to change the title, since it's a bit long for a sidebar menu.

[andreasnilssondev]

Hi,

Just thought I'd mention a few things while new docs are being worked on, and I recently got setup again (last time was a few months ago). I think it's important being able to connect netlify-cms as quickly as possible, so people don't give up and go somewhere else.

• I copied an example config.yml from the docs that contained widget: "foo". This broke for me but I didn't realize why (no helpful error message). I think the config.yml should contain only the minimum amount of code to get a working example. It could maybe then link to a part with all the config explanations?
• In collections, when setting a folder, to for example public/_posts, it seems to be necessary for the _posts folder to exist. This could be communicated more clearly since it's not the first thing you think about when starting fresh and don't have any posts. I expected it to be created automatically if it didn't exist, and it's not straight forward for everyone how to publish an empty folder to git.

[erquhart]

@nAndreas regarding the three issues in your comment (so late here, sorry):

1. Widget "foo" in the docs has been removed
2. Folders are created automatically (I believe they have been from before this issue), please provide repro steps
3. If a non-existing widget is specified, the editor UI says something like "editor 'foo' not found" right in the editor, and it doesn't break. What break did you experience?

[ragasirtahk]

How about adding a section about configuring and using the CMS with multiple authors?

[erquhart]

We should probably have a lot of specific setups (like multiple authors) documented. We think of it as being so simple that it isn't necessary - for instance, every Netlify CMS instance is multi-author by default, whoever is logged in is the author - but writing it out in the docs is compelling.

[stale]

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.

[martinjagodic]

Closing as stale and/or outdated.