Polyfill for Object.values

[kungfooman]

Right now not every code path is polyfilled, for example this doesn't work in IE11:

test = new pc.Entity('test');
test.addComponent('anim');
test.anim.dirtifyTargets();

Because of Object.values:

engine/src/framework/components/anim/component.js

Lines 274 to 279 in a69aa61

	dirtifyTargets() {
	const targets = Object.values(this._targets);
	for (let i = 0; i < targets.length; i++) {
	targets[i].dirty = true;
	}
	}

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[willeastcott]

Since @ellthompson is the originator of these calls to Object.values, I've assigned this PR to him. 😄