- Move from CommonJS to ESM.
- Fix `__dirname` and `__filename` use.
- Bump package version to v2.0.0.

Ie. `[absolute local link](/absolute/path/to/file.md)`.

Regular mode shows all processed files and all valid and invalid links in them.

Quiet mode (`-q` or `--quietMode`) shows only files with invalid links.

Refs: webhintio#6

Regular mode flags as invalid all local links without `.md` extension.

With this option (`-e` or `--optionalMdExtension`) also links without extension (ie. `./path/to/file` instead of `./path/to/file.md`) are checked and can be valid.
They can be also folders with an `index.md` file inside.

Regular mode flags as invalid all local links without extensions other than `.md`. Links in image tags are ignored (ie. `![]()`).

With this option (`-o` or `--allowOtherExtensions`) also links with extensions other than`.md` (ie. `./path/to/file.txt`, but also images) are checked and can be valid.

Fix vulnerabilities overriding nested dependencies.

Refs: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substr

…tion

Refs: webhintio#7