Centralize and elevate configuration documentation

[jmooring]

This would be a major change, so we should not act on this without bep's approval.

Currently the configuration documentation is spread around throughout the site. I propose creating a section for configuration, with a page for each of the configuration tables: root, markup, taxonomies, menus, params, etc.

This section would be located near the bottom, as a reference. It would be nice if docs.json, generated from source, contained the defaults for all of the keys.

Also incorporate intent from:

• Document setting of params, etc from themes #427
• Add services config page #1781
• Document services config #1779
• Document use of configuration environment variables #2154
• Improve config merge section #2186
• Document the differences between highlight shortcode and code fence attributes #1628

High level keys:

• intro
• all
• build
• caches
• cascade
• contentTypes (#2922)
• deployment
• frontmatter
• httpcache
• imaging
• languages
• markup
• mediatypes
• menus
• minify
• module
• outputformats
• outputs
• page
• pagination
• params
• permalinks
• privacy
• related
• security
• segments
• server
• services
• sitemap
• taxonomies
• uglyurls

Other:

• Add note about per-language configuration

[bep]

This section would be located near the bottom, as a reference. It would be nice if docs.json, generated from source, contained the defaults for all of the keys.

I think the above is true now.

As to this issue, I somehow didn't notice it before now, but I certainly agree that creating a section for configuration would make perfect sense.