* Pass `dirname` as extra metadata to preset constructor. Sometimes a preset would like to know where it should resolve relative paths from (e.g. https://github.com/tleunen/babel-plugin-module-resolver) and this extra information makes that possible. * Test for `dirname` passed into preset constructor This adds a check for `dirname`’s existence and correctness to the `resolve-addons-relative-to-file` test, and serves as a minimal example of a path-aware preset.