Add monorepo support with new option to allow relative paths

[santiagodiaz]

What & Why:

When using the github-codeowners tool in a monorepo, we can see an issue when installing the tool in a subdirectory and trying to use the tool commands for the root of the repository.

This is the error when using a command like audit or who:

failed to run audit command RangeError: path should be a `path.relative()`d string, but got "../.dockerignore"

This is caused because of ignore package not accepting file paths like this:

/foo,
./foo,
../foo,
.
..

This PR:

• Updates ignore package to 5.2.0 version.
• Adds new option -a, --allow-relative-paths allow relative paths (default: false)
  • This option allows us to place the tool in any subdirectory and audit file paths that were not accepted before