Adding support for helm charts

[robaiken]

What are you trying to accomplish?

Adding support for Helm charts files in dependabot-core. This will allow Dependabot to handle dependency updates in Helm files.

How will you know you've accomplished your goal?

Dependabot successfully detects and updates dependencies in helm manifest files automatically.

Checklist

• I have run the complete test suite to ensure all tests and linters pass.
• I have thoroughly tested my code changes to ensure they work as expected, including adding additional tests for new functionality.
• I have written clear and descriptive commit messages.
• I have provided a detailed description of the changes in the pull request, including the problem it addresses, how it fixes the problem, and any relevant details about the implementation.
• I have ensured that the code is well-documented and easy to understand.