use url equivalence excluding fragments for id comparison

[philloooo]

The https://url.spec.whatwg.org/#url-equivalence defaults to exclude fragments = false. Clarify in id member that the equality comparison here excludes fragments.

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[marcoscaceres]

I think we need to move this part up to the processing the manifest section.

It should go:

21. Process the id member passing json, manifest and document URL.
22. If document's [=processed manifest=] is not null:
    22.1 If [=processed manifest=]["id"] member is not [=url/equal|equals=] with exclude fragment true to |manifest|["id"], then return. (We might need a note here to clarify if anything should happen when there is a mismatch - it's not an error, we just drop the new manifest on the floor).
    22.2 If ???? members have changed, signal to the end user that manifest is a replacement for the already-installed application's manifest.
23. Let document's processed manifest be manifest.

Now 22.2 might have special rules, like:

• How do we actually if the manifest has changed? Do we JSON-serialize them and do text comparisons?
• what happens if the scope changes, and the current page is out of scope?
• Is there any situation where we can do a silent update? (e.g., only the theme-color changed... my gut feeling is no).
• If the icons change, do we need to say MUST prompt? What else would should cause a prompt?

Do we need final step "24", that once we have updated the manifest, we need to re-apply the manifest. However, that causes the entire application to reload... what does that mean? Do we need to navigate back to the start URL?

[philloooo]

Merged this to #1011