Related Issue(s): None

Proposed Changes:

Clarified which media types should be used for the hierarchical relation types.

Intention is to make clients more aware of checking media types as with OGC API - Records etc. we'll run more and more into examples where the media types could be different.

Example with a child link with JSON & HTML media types: https://api.weather.gc.ca/stac/?f=json
or as a JSON excerpt:

{
   "type":"Catalog",
   ...
   "links":[
      {
         "rel":"child",
         "href":"https://api.weather.gc.ca/stac/msc-datamart?f=json",
         "type":"application/json"
      },
      {
         "rel":"child",
         "href":"https://api.weather.gc.ca/stac/msc-datamart",
         "type":"text/html"
      }
   ]
}

Nothing in the spec disallows this, I think.
And we should not disallow it iMHO, to keep compliant with OGC API - Records.

PR Checklist:

• This PR is made against the dev branch (all proposed changes except releases should be against dev, not master).
• This PR has no breaking changes.
• I have added my changes to the CHANGELOG
  or a CHANGELOG entry is not required.
• This PR affects the STAC API spec,
  and I have opened issue/PR #XXX to track the change.