mapping for denoland/dnt about event

[UrielCh]

issue solved
with the dnt config:

await build({
    entryPoints: ["./mod.ts"],
    outDir: "./npm",
    shims: {
      deno: true,
      webSocket: true,
      undici: true,
      custom: [
        {
          package: {
            name: "stream/web",
          },
          globalNames: ["ReadableStream", "TransformStream"],
        },
        {
          globalNames: [ {name: "MessageEvent", typeOnly: true} ],
          package: {
            name: "ws",
          },
        }
      ],
    },
    compilerOptions: {
      lib: [ "dom", "esnext" ],
    },
...