Esbuild IIFE doesn't export a global name

[fasiha]

Need to use https://esbuild.github.io/api/#global-name somewhere in

mudderjs/esbuild.mjs

Lines 5 to 11 in d83942d

	await build({
	entryPoints: ["index.js"],
	outfile: "dist/mudder.min.js",
	sourcemap: true,
	minify: true,
	format: "iife",
	});

Discovered this by putting <script src="mudder.min.js"></script> in a HTML file and copying the JS and source map to the same directory and realizing nothing in it was exporting a mudder top-level global variable, oops.

Also cf., #18.