Fix regression in how array input values are transformed

[mattt]

Resolves #265

#184 introduced a regression in how array input values are serializes.

replicate-javascript/lib/util.js

Lines 312 to 319 in e059286

	if (Array.isArray(value)) {
	let copy = [];
	for (const val of value) {
	copy = await transform(val, mapper);
	}
	return copy;
	}

This PR fixes the logic to append transformed values to the array instead of copying them.

replicate-javascript/lib/util.js

Lines 312 to 319 in ae68faa

	if (Array.isArray(value)) {
	const copy = [];
	for (const val of value) {
	const transformed = await transform(val, mapper);
	copy.push(transformed);
	}
	return copy;
	}