JavaScript module file xxx.mjs has no content-type definition when serving static files

[simon639]

mime-types.lisp

mime-type-list
("text/javascript" "js")
("text/javascript" "js" "mjs")

Chrome Error Message:
app.mjs:1 Failed to load module script: Expected a JavaScript module script but the server responded with a MIME type of "application/octet-stream". Strict MIME type checking is enforced for module scripts per HTML spec.