generateImages() function does not return a Promise

[jetxr]

Describe the bug
generateImages() function is async and type hints that it will return a Promise but does not return a Promise.

pwa-asset-generator/src/main.ts

Lines 119 to 124 in aadbb9b

	return {
	savedImages,
	htmlMeta,
	manifestJsonContent,
	};
	}

Expected behavior
generateImages() should return a Promise that gets resolved with the value of type Result.

Why

• While using await generateImages in a CD environment, I cannot do process.exit() as shown in the examples.
• Current implementation causes the following example to just wait without exiting gracefully

import {generateImages} from "pwa-asset-generator";

await generateImages('input.svg', './output', {
    type: 'png',
});

await generateImages('input.svg', './output', {
    type: 'jpg',
});

System (please complete the following information):

• OS: macOS Ventura
• node version: 18.4
• npm version: 9.3.1
• cli version: 6.2.1

Additional context
Thankully Github Actions terminated the script after 6 hours :)