GraphQL: Add docs for quote endpoint in 2.3.1

[keharper]

Community engineering issue

Type of Doc:

• New topic
• Topic Update, Devdoc link: https://devdocs.magento.com/guides/v2.3/graphql/reference/quote.html
• Other

Magento 2 GitHub Issue: Various. See the links within the graphql-ce PRs

Magento 2 GitHub PRs:
magento/graphql-ce#163
magento/graphql-ce#170
magento/graphql-ce#192
magento/graphql-ce#211
magento/graphql-ce#266

Magento 2 version:

• 2.1.X
• 2.2.X
• 2.3.1
• back port
• forward port

Notifications of Changes:

• Changes to Admin interface?
• New software requirements?
• New REST endpoints or updated GraphQL query syntax?
• New command line option?

Content

Several PRs that add mutations for the quote endpoint have been checked in recently. This issue tracks the documentation effort from one place.

Additional information

This PR contains tests that might prove useful.

https://github.com/magento/graphql-ce/pull/240/files

[keharper]

This issue is now being tracked here:

magento/graphql-ce#588