fix backward compability for cjs exports

[ffortier]

Fixes #40

Some files were missing from the repos, so I had to put place holders for tsconfig.json, tsconfig-esm.json, tsconfig-cjs.json and fixup.sh.

When loading from a cjs import, mkdir will be available directly instead of being wrapped in a es6 module.

[isaacs]

Ah, how embarrassing that my old .gitignore file was keeping those out, I didn't notice that in the rewrite.

What you did here was surprisingly close to what I already had in place, and I was able to incorporate it pretty easily. Having an index-cjs that just re-exports the default is really clever, and saves the whole require('mkdirp').default wart, I love it! I'm going to copy this in my other hybrid modules.

[isaacs]

Shipped on v2.1, thanks for the trick!