Adds stretchMetadata option to generateLayout functions

[jaericson]

Adds stretchMetadata as an optional option to generateLayout and generateLayoutUnique. If set to true, the resulting layout object will contain the following stretch metadata properties, if present: content, stretchX, and stretchY.

This leverages work from https://github.com/mapbox/spritezero/pull/68.

• [ ] Is there any reason we should make the default instead be to include stretch metadata, if present? (As opposed to the default being not to include it in the layout object.)

TODO:

• [x] Add unit tests

[jaericson]

Whoops, looks like it's complaining about the spread operator usage. Maybe I need to revert back to using xtend?

[jseppi]

Whoops, looks like it's complaining about the spread operator usage.

Looks like eslint is what is having the problem. I think there's a way to fix that.

[jseppi]

Yeah, adding this to .eslintrc will do it:

    "parserOptions": {
        "ecmaVersion": 2018
    },

ref https://eslint.org/docs/user-guide/configuring#specifying-parser-options

[jseppi]

Is there any reason we should make the default instead be to include stretch metadata, if present?

👍 I'd be happy with it being enabled by default

[jaericson]

I'd be happy with it being enabled by default

@jseppi Great! Do you think we should rename the property to something like ignoreStretchMetadata so that omitting the property still means false?

[jseppi]

Do you think we should rename the property to something like ignoreStretchMetadata so that omitting the property still means false?

oof, that's a long name!

I don't actually have a strong preference, but I think you could also keep it as stretchMedata and defult to true by doing something like this:

options.stretchMedata = options.stretchMetadata !== undefined ? options.stretchMetadata : true