chore: add credo fixes

[vitor-mda]

Hey there!

Introducing a few Credo-related changes:

• bump Credo version to 1.7.7
  • when running Credo with Elixir 1.18, a CaseClauseError was being raised. This issue was tracked and fixed on Credo's repo, and seems to happen as of Elixir version 1.17. The fix was released on Credo version 1.7.7.
• Add Credo config file, disabling the Readability.ModuleDoc check
  • since every module has a @moduledoc false doc, there is no point in having this enforced style check, right?
• remove false @moduledocs and update hardcoded line reference in test
  • one of the tests has a hard coded line reference which decreased by 1 after removing one of the @moduledoc false lines.
• fix Readability.PredicateFunctionNames credo check violation
  • change is_range? function name to range?, following the Readability.PredicateFunctionNames style for predicate functions.