Adds requirements specifying need for Libyaml on Linux. Closes: #121 (#122)

* Updated CONTRIBUTING.md to show requirements.

* removed Gemfile.lock

* Apply suggestions from code review

---------

Co-authored-by: Juan Vásquez <[email protected]>

Author: FiggyFoxFunc

CONTRIBUTING.md

@@ -14,6 +14,12 @@ Here's what you need to do:
 - [Make sure the test suite passes on GitHub Actions and make any necessary changes to your branch to bring it to green.](#continuous-integration).
 - Check out the [Help Wanted](#help-wanted) section for suggestions on how to support Skunk.
 
+## Requirements
+For a Linux distro called Pop!_OS, running Ruby 3.0 and up might require installing the following packages:
+```bash
+sudo apt install libyaml-dev
+```
+
 ## Setting up your environment
 To install the dependencies, run:
 
@@ -81,4 +87,4 @@ The SkunkScore of a module should be the average of the SkunkScores of all of it
 
 Feel free to review and submit your suggestions to improve the method [RubyCritic::AnalysedModule#skunk_score](https://github.com/fastruby/skunk/blob/main/lib/skunk/rubycritic/analysed_module.rb#L33).
 
-📘 Read [Escaping The Tar Pit: Introducing Skunk v0.3.2 at RubyConf 2019](https://www.fastruby.io/blog/code-quality/escaping-the-tar-pit-at-rubyconf.html) and [Churn vs. Complexity vs. Code Coverage](https://www.fastruby.io/blog/code-quality/churn-vs-complexity-vs-coverage.html) for more details about the `skunk_score` method.
+📘 Read [Escaping The Tar Pit: Introducing Skunk v0.3.2 at RubyConf 2019](https://www.fastruby.io/blog/code-quality/escaping-the-tar-pit-at-rubyconf.html) and [Churn vs. Complexity vs. Code Coverage](https://www.fastruby.io/blog/code-quality/churn-vs-complexity-vs-coverage.html) for more details about the `skunk_score` method.