chore(joint-core): replace rollup buble with rollup babel

[jamesgeorgewilliams]

Description

Replace rollup buble with rollup babel. Added comment about failing case.

Motivation and Context

This allows the user to write newer ES features in src code.

Notes:

• karma and uglify dependencies were updated in order to run without errors for ES6 code.
• utilHelpers.mjs update

As everything isn't transpiled to ES5 anymore, we had an error in the following tests:

joint/packages/joint-core/test/jointjs/utilHelpers.js

Lines 1382 to 1416 in 58df31d

	QUnit.test('should compare sets', function(assert) {
	const set1 = new Set();
	const set2 = new Set();
	set1.add(1);
	set2.add(2);
	assert.strictEqual(joint.util.isEqual(set1, set2), false);
	set1.add(2);
	set2.add(1);
	assert.strictEqual(joint.util.isEqual(set1, set2), true);
	set1.delete(1);
	set1.add(1);
	assert.strictEqual(joint.util.isEqual(set1, set2), true);
	set2.delete(1);
	assert.strictEqual(joint.util.isEqual(set1, set2), false);
	set1.clear();
	set2.clear();
	});
	QUnit.test('should compare sets with circular references', function(assert) {
	const set1 = new Set;
	const set2 = new Set;
	set1.add(set1);
	set2.add(set2);
	assert.strictEqual(joint.util.isEqual(set1, set2), true);
	set1.add(1);
	set2.add(2);
	assert.strictEqual(joint.util.isEqual(set1, set2), false);
	});

The let causes a reference error in the following lines. This was working previously because it was transpiled to var. This change updates to an explicit use of var.

joint/packages/joint-core/src/util/utilHelpers.mjs

Lines 680 to 685 in 58df31d

	case mapTag:
	let convert = mapToArray;
	// Intentional fallthrough
	// eslint-disable-next-line no-fallthrough
	case setTag:
	convert || (convert = setToArray);

Lodash is now using TS, but was using var in previous JS code.
https://github.com/lodash/lodash/blob/c6e281b878b315c7a10d90f9c2af4cdb112d9625/_equalByTag.js#L82