fix: shorthand transition and animation params

[bfanger]

Real fix for #785

I've updated the REPL to make it extra clear what is happening.

Directive	Nr. args	Empty object
use	1	false
use={{}}	2	true
animate	3	true
animate={}	3	true
animate={{duration}}	3	false
transition	2	true
transition={{}}	2	true
transition={{duration}}	2	false

This demonstrates that unlike the use shorthand, the transition and animate shorthand pass an empty object as parameter.
<div transition:fade> is identical to <div transition:fade={{}}> as far as the svelte compiler is concerned.

This allows custom transitions like svelte-transitions-fade-scale:

function fadeScale(node, { delay = 0, duration = 200, easing = x => x, baseScale = 0 })

to work as shorthand <div transition:fadeScale> without causing Cannot read property 'duration' of undefined errors.

In svelte 3.32.0 the params got an empty object as default value = {}, this change hides the fact that svelte2tsx created the wrong type for the built-in transitions, silencing the "Expected 2 arguments, but got 1." error reported by svelte-check
(This is still a nice change, it makes reusing the built-in transitions with defaults easier)

[dummdidumm]

I didn't initially always add the empty object because my fear is that people would create custom transitions/animations which don't expect an object as second parameter. Then again, since the compiler adds this in case nothing is passed in, I guess this change makes sense.