How to use esbuild with css import assertions/attributes

I've code where some librarys import css without a assertion or a with attribute:

import aaSheet from "aa.css";

this works, but if I have this code:

import bbSheet from "bb.css" assert {type: 'css'};

or this:

import bbSheet from "bb.css" with {type: 'css'};

then the type of bbSheet hast to be a CSSStyleSheet, but esbuild does not create one.
And I don't know in the onResolveCallback if the "assert" or "with" attribute is present (the assert keyword was changed to with, but it should be nearly the same), so I don't know how I could create a plugin

Start by tracing esbuild's handling of JavaScript import assertions and import attributes, including the onResolveCallback behavior described in the issue. Determine the intended output for CSS imports with type: 'css', and consider how completion would be verified for both assert and with syntax.

Written by the indexing model from the issue text.