allow for ES6 Object property shorthand

[GGAlanSmithee]

In the below example, when POSTing data:

on end(item, oldIndex, newIndex) fetch /sort { method: 'post', body: { id: item@hx-id, oldIndex: oldIndex, newIndex: newIndex } as JSON }

it would be nice to be able to use ES6 object property shorthand notation:

on end(item, oldIndex, newIndex) fetch /sort { method: 'post', body: { id: item@hx-id, oldIndex, newIndex } as JSON }

(the difference being that { oldIndex: oldIndex, newIndex: newIndex } becomes { oldIndex, newIndex })

I have no insight into how doable this it, but the rule is quite constrained, since it's only valid in a { ... } block