docs: add absolute links to CONTRIBUTING from README (#2934)

README.md

@@ -486,9 +486,9 @@ gem 'faker', :git => 'https://github.com/faker-ruby/faker.git', :branch => 'main
 
 ## Contributing
 
-**Note**: We are not accepting proposals for new generators and locales. The [Contributing](CONTRIBUTING.md) guide has a few notes about this decision.
+**Note**: We are not accepting proposals for new generators and locales. The [Contributing](https://github.com/faker-ruby/faker/blob/main/CONTRIBUTING.md) guide has a few notes about this decision.
 
-Take a look at the [Contributing](CONTRIBUTING.md) document for
+Take a look at the [Contributing](https://github.com/faker-ruby/faker/blob/main/CONTRIBUTING.md) document for
 instructions on setting up the repo on your machine, opening bug reports, understanding the codebase,
 and creating a good pull request.