Add option to sort shorthand props on jsx-sort-props

[lucasmotta]

You can now require that shorthand props should come before all other props, but still respecting the alphabetical order.

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The following are valid situations:

<Component a b="b" />
<Component x z a="a" b="b" />

And the following are invalid:

<Component z x a="a" b="b" /> // should be in alphabetical order
<Component x z b="b" a="a" /> // should be in alphabetical order
<Component a="a" b="b" x z /> // shorthand props should be at the start

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• Tests
• Backwards compatibility

[yannickcr]

Great, thanks!