Method add

src/animate/Keyframes.js:19–63

(...rest)

	 * myKeyframes.add('20%', alpha, 1);
	 */
	add(...rest) {
		if (!rest.length) return;

		if (typeof rest[0] === 'object') {
			const keyframe = rest[0];

			for (let key in keyframe) {
				const timevalue = keyframe[key];
				let time;

				if (Utils.isNumber(key)) {
					time = key + '%';
				} else {
					time = key.indexOf('%') > -1 ? key : key + '%';
				}

				delete keyframe[`${key}`];
				keyframe[time] = timevalue;
				this.setColor(keyframe[time]);
			}

			Object.assign(this.keyframes, keyframe);
		} else {
			let time = Utils.isNumber(rest[0]) ? rest[0] + '%' : rest[0];
			let keyframe = {};
			let style;
			let value;

			if (rest.length === 3) {
				style = rest[1];
				value = rest[2];

				keyframe[time] = {};
				keyframe[time][style] = value;
			} else {
				value = rest[1];
				keyframe[time] = value;
			}

			this.setColor(keyframe[time]);
			Object.assign(this.keyframes, keyframe);
		}

		this.fill();
	}

	get(time) {
		if (Utils.isNumber(time)) time = time + '%';