Use Python to simply server files from local dir, giving javascript the correct MIME type.

httpServer.py

# Use to create local host, server javascript modules w/the correct mimetime.
# See https://stackoverflow.com/a/60638762
# 
import http.server
import socketserver

PORT = 8080

Handler = http.server.SimpleHTTPRequestHandler
Handler.extensions_map.update({
    ".js": "application/javascript",
})

httpd = socketserver.TCPServer(("", PORT), Handler)
httpd.serve_forever()