Document of syntax in manifest.yml

[duynguyen]

We don't have yet a complete document of the grammar in manifest.yml file. The closest is wskdeploy docs but they are not exactly the same. We should have a complete doc for this in project Firefly, tentatively part of https://github.com/AdobeDocs/project-firefly/blob/master/guides/app-hooks.md.

[duynguyen]

This is also a good inclusion: adobe/aio-cli#207.

[sarahxxu]

Configuring action timeout in manifest

actions:
  generic:
    function: actions/generic/index.js
    runtime: 'nodejs:12'
    limits:
      timeout: 1800000

[Himavanth]

adobe/aio-cli-plugin-runtime#200 needs to be included in the syntax doc

[shazron]

This is also a good inclusion: adobe/aio-cli#207.

related: apache/openwhisk-wskdeploy#1107