Consider moving away from Gulp

Why?

• gulpjs upstream hasn't had any new commits since Dec 2022. The project is not officially dead (of course), but the development has been slow.
• The JS code for the gulp tasks in this repo is pretty complex (for someone new to JS like me to understand and fork a custom theme of).

What should we use instead?

vitejs seems to gain quite a lot of traction lately. I'm no where familiar with either gulp or vite, but from the surface it looks like a good alternative.

There is a plugin to handle Handlebar templates (https://github.com/vituum/vite-plugin-handlebars). For the building preview task, we might need to implement ourselves, as we currently do with gulp.

Pros:

• Has a lot of functionalities baked in, so we don't need to reinvent the wheel
• Seems to be pretty fast

Cons:

• Opinionated (things may work the way we don't like it to)