[AG-38] Parse Ruby gemspec package descriptors

[felipead]

We need to parse and extract dependencies from *.gemspec files which are deeply nested inside the repositories and included in Gemfiles. For example, this file is being imported by the main Gemfile:

https://github.com/acme/example/blob/master/foo/bar/foo_bar.gemspec

I've found many other examples where gemspec files are declared in Ruby repositories, so we need to parse them and include the dependencies in the report.