Provide option to specify configuration file for `doc-changelog` action

[klmcadams]

📝 Description of the feature

For repositories containing a pyproject.toml and towncrier.toml, allow the user to specify using the towncrier.toml file. Currently, if both of these files exists it automatically defaults to the pyproject.toml

Requested by @ansjhenry

💡 Steps for implementing the feature

Add an optional input to the doc-changelog action to specify the name of the configuration file. By default, it will be pyproject.toml

🔗 Useful links and references

No response