The Alpine.js you downloaded from the CDN is not a module.
When I tried it the way you did, esbuild complained exactly about that.
If you want to use it as a module, then you need to either use npm to isntall it or clone from GitHub and build it, though it has dependencies, which are usually pulled from NPM (the service).
There might be ways to vendor them, though that will again require extra work, and might recurse infinitely, as dependencies have the habbit to also have dependencies.
Okay, I have to admit, the list is short for alpine, its about a handfull of deps. But its still annoying.
So perhaps you can use npm (the tool) or yarn to use alpine from GitHub? Though I am not sure how that will deal with dependencies and if you can override transient dependencies to use GitHub instead of NPM (the service).
