`eszip extract` fails when a specifier in the eszip has no path or is a directory of another specifier

[dsherret]

The code here:

eszip/lib/eszip.ts

Line 89 in c9e9144

await write(join(dest, "source", url2path(specifier)), module);

...is very basic and looks at the pathname only to figure out how to extract.

This will fail in two scenarios:

1. Where there is no path, like https://fresh.deno.dev
2. A path is a directory of another specifier. For exmaple: something/ then something/other.ts