add update animation name feature

[MFrozenM]

When you want to update the animation name in Transition, it doesn't work.

<Transition name={animation}> {active() === 0 && <Component/>} </Transition>

The problem was mergedProps. It doesn't update when we pass a new name with props.
So, I remove it, declare the classes with let, and handle name changes in createEffect.

[thetarnav]

I think that removing the mergeProps is a good call—it's not necessary for anything.
Deriving the class names via effect will work for most cases, but shouldn't it be derived with createComputed, or better createMemo instead?
The animation is being handled by createComputed on line 128 which will run before this createEffect if both were to be triggered at the same time.

Suggested change

	createEffect(() => {
	// effect if the name of animation changes
	const name = props.name || "s";
	// declare classes with new name property
	enterActiveClass = name + "-enter-active"
	enterClass = name + "-enter"
	enterToClass = name + "-enter-to"
	exitActiveClass = name + "-exit-active"
	exitClass = name + "-exit"
	exitToClass = name + "-exit-to"
	})
	const classnames = createMemo(() => {
	const name = props.name || "s";
	return {
	enterActiveClass: name + "-enter-active",
	enterClass: name + "-enter",
	enterToClass: name + "-enter-to",
	exitActiveClass: name + "-exit-active",
	exitClass: name + "-exit",
	exitToClass: name + "-exit-to",
	};
	});

[MFrozenM]

Yes, this is a better idea.
I checked it and it worked.
I close this PR and open another adding your suggestion and some other changes.