Reorganize navigation items in docs

[stevepiercy]

The docs are rendered as a huge flat list, with not enough thought for organization. I propose to organize and sort them as follows.

• Put endpoint docs into new directory endpoints/.
• Put usage docs into new directory usage/. These include items that span the endpoints.
• Create a new contributing directory for how to contribute.

introduction  # has toctrees for content-negotiation and plone-content

usage/
    authentication
    batching
    content
    customization
    exploring
    i18n
    serialization
    sharing
    types-schema
    blocks

endpoints/
    actions
    addons
    breadcrumbs
    comments
    contextnavigation
    controlpanels
    copymove
    database
    email-notification
    email-send
    expansion
    groups
    history
    locking
    navigation
    portrait
    principals
    querystring
    querystringsearch
    registry
    roles
    searching
    system
    tiles
    translations
    tusupload
    types
    users
    vocabularies
    workflow
    workingcopy

upgrade-guide

contributing -> contributing/index
contributing/
    index
    conventions

Please let me know what y'all think. Thank you!

[jensens]

Lgtm

[davisagli]

Looks like a good improvement to me.

I am not sure if we should add contributor docs here, or if plone.restapi should be mentioned as a special case in the top-level contributor section (i.e. the one in plone/documentation that I still need to work on). I guess it makes sense to add a section here, and then mention it with a link from the top level contributor docs.

[stevepiercy]

I am not sure if we should add contributor docs here, or if plone.restapi should be mentioned as a special case in the top-level contributor section (i.e. the one in plone/documentation that I still need to work on). I guess it makes sense to add a section here, and then mention it with a link from the top level contributor docs.

You got it, I mean, the latter. See https://github.com/plone/documentation/issues/1278

[stevepiercy]

There's a weird one that looks like it should be in endpoints, but is placed under Introduction.

https://plonerestapi.readthedocs.io/en/latest/plone-content.html

I think that it should be entitled "Content Types", renamed to content-types.md, and moved into endpoints. I will do that in the PR, but if you have a different opinion, please speak up.

[stevepiercy]

I am also going to merge the content-negotiation page into the introduction page. Its content is minimal, and a separate page for introductory stuff is unusual. It also renders a strange collapsible navigation that is not necessary.