feat: make options for appendAnimation and detachAnimation optional

[Frank3K]

Description

This PR makes all parameters of AppendAnimationOptions and DetachAnimationOptions optional.

Such that the following is possible:

// Example: Only specify repetitions
appendAnimation('some-animation', { repetitions: 5 });

// Example: Only specify fade for detach
detachAnimation('some-animation', { fade: 200 });

Previously, you had to pass all options, or no options at all (in case the default was used). Current code in master:

model-viewer/packages/model-viewer/src/features/animation.ts

Lines 33 to 41 in 4efaf8e

	interface AppendAnimationOptions {
	pingpong: boolean, repetitions: number|null, weight: number,
	timeScale: number, fade: boolean|number, warp: boolean|number,
	relativeWarp: boolean, time: number|null
	}
	interface DetachAnimationOptions {
	fade: boolean|number
	}

@mohammadbaghaei Would you be so kind to do the review? I tried to use appendAnimation, but then I was a bit surprised I needed to pass all parameters. I have no real experience with these methods, so it would be nice if you can take a look and functionally test.

Reference Issue

[Frank3K]

@mohammadbaghaei I am particularly not 100% sure about this line.