Fix: Avoid end_offset overflows

[ofeefo]

This pull request addresses a potential bug in the YAML editor by ensuring that the YAML data always ends with a trailing newline, and adds a regression test to prevent end offset overflow errors when updating YAML values.

Bug fix for YAML data handling:

• Ensures that the @data string in PatchYAML::Editor#reload always ends with a newline character to prevent parsing issues, which could lead to end offset errors. (lib/patchyaml/editor.rb)

Testing and regression prevention:

• Adds a regression test in regression_spec.rb to verify that updating a YAML structure does not cause an end offset overflow, and that the output remains correct. (spec/regression_spec.rb)

[heyvito]

Merging with errors, RuboCop offenses will be fixed later on.

Thanks @ofeefo!