[w3c/manifest] Adding field `display_override` to the manifest (#932)

Closes #???
I'm not sure there is one, but it is related to #856 and could close that - but that issue also goes over some other pieces that this change doesn't solve for yet.

This change (choose at least one, delete ones that don't apply):

* Adds new normative recommendations or optional items

Implementation commitment (delete if not making normative changes):

* [ ] Safari (link to issue)
* [x]  Chrome (link to issue): https://bugs.chromium.org/p/chromium/issues/detail?id=1092667
* [ ] Firefox (link to issue)
* [x] Edge (public signal): https://bugs.chromium.org/p/chromium/issues/detail?id=1092667 (they are doing the implementation work)

If change is normative, and it adds or changes a member:

* [ ] [updated JSON schema](https://github.com/SchemaStore/schemastore/blob/master/src/schemas/json/web-manifest.json)

**I have not done this yet - should I do this before this request is filed?**

Commit message:

Adds the "display_override" manifest field.

This field allows the developer to override the "display" field with a custom fallback chain. It is designed to be both future- and backwards-compatible, and is basically just a logic/algorithm change on how a user agent should determine the requested display mode.

This change also creates an explicit algorithm for determining the display mode, and provides a few new examples using "display_override".

Person merging, please make sure that commits are squashed with one of the following as a commit message prefix:

* chore:
* editorial:
* BREAKING CHANGE:
* **And use none if it's a normative change**


<!--
    This comment and the below content is programatically generated.
    You may add a comma-separated list of anchors you'd like a
    direct link to below (e.g. #idl-serializers, #idl-sequence):

    Don't remove this comment or modify anything below this line.
    If you don't want a preview generated for this pull request,
    just replace the whole of this comment's content by "no preview"
    and remove what's below.
-->
***
<a href="https://pr-preview.s3.amazonaws.com/dmurph/manifest/pull/932.html" title="Last updated on Jul 28, 2020, 6:19 PM UTC (1a3587c)">Preview</a> | <a href="https://pr-preview.s3.amazonaws.com/w3c/manifest/932/d767baf...dmurph:1a3587c.html" title="Last updated on Jul 28, 2020, 6:19 PM UTC (1a3587c)">Diff</a>
You can view, comment on, or merge this pull request online at:

  https://github.com/w3c/manifest/pull/932

-- Commit Summary --

  * Adding display_override manifest field
  * updated with examples & formatting

-- File Changes --

    M index.html (95)

-- Patch Links --

https://github.com/w3c/manifest/pull/932.patch
https://github.com/w3c/manifest/pull/932.diff

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/w3c/manifest/pull/932