> a top-level "browser" field should point to CJS files that, when bundled by a non-broken module bundler, work in a browser

https://github.com/browserify/browser-resolve/pull/101#issuecomment-806391082

I've changed the `browser` field to point to the `cjs` version of this module in
line with the above comment because this module is currently broken when used with
browserify.

I've also added the [util](https://www.npmjs.com/package/util) module as a dep since it's used
in the code. It would be ignored in most environments so the only cost is a slightly larger
bundle but it's likely to be included in any non-trivial bundle somewhere anyway so there's
likely to be no real-world impact.

Also:

- Adds typescript dep to tests that test typescript, otherwise tests fail with
  'cannot determine executable to run' - unless you have tsc installed globally I guess?
- Fixes a typo in a comment
- Simplifies .gitignore

Fixes #19