Add object-fit and object-position

[jamesnw]

They both use caniuse: object-fit, but I'm not sure if multiple features can share a feature key.

Also adds missing object-view-box key.

[autonome]

Yes, seems not right to have >1 Caniuse mapping, I posted to the channel for broader discussion and input.

The only other comment I have is around the replaced element terminology, which seems more on the spec language end of the spectrum than developer/designer POV (esp new learners). If you're using that everywhere already, then maybe not an issue (or a broader one), but doesn't block merging this either way.

[ddbeck]

On the caniuse question @autonome highlighted:

Narrowly, caniuse mappings should be one-to-one or one-or-many. As far as I know, we have no features yet that are many-to-one. It would be unhelpful to show multiple statuses for a single caniuse feature, so I think many-to-one also doesn't make sense. I think we ought to pick one of these to have the caniuse mapping and drop it from the other.

In the future, when we have feature composition nailed down, a feature combining object-fit and object-position is a natural follow on and a place to move the caniuse mapping. Honestly, I see why this is is a single feature on caniuse. Imagine if there was an object shorthand property; this would be easy to put down as a single feature.

Long-term, I'd like it if web-features could take any reasonable address/identifier (e.g., caniuse's object-fit) and resolve a feature (if we have one) or an anonymous slice of a feature (if we don't).

[ddbeck]

I endorse "replaced element" here—you've already said what it is through examples, so we're doing a little developer education while we're at it.

[ddbeck]

Cheers!