feat(resolver): Add support for extracting and processing text file attachments in GitHub issues

[oconnorjoseph]

This change introduces methods to:

• Extract text file attachments from issue bodies
• Download and retrieve contents of attached text files
• Incorporate attachment contents into issue context for processing
• Enhance issue handling with additional context from file attachments

The implementation includes new methods for parsing Markdown links, downloading files, and integrating their contents into the issue processing workflow.

End-user friendly description of the problem this fixes or functionality that this introduces

• [x] Include this change in the Release Notes. If checked, you must provide an end-user friendly description for your change below

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Give a summary of what the PR does, explaining any non-trivial design decisions

This PR enhances the Resolver to be able to extract and process text file attachments in GitHub issues.

This change introduces methods to:

• Extract text file attachments from issue bodies
• Download and retrieve contents of attached text files
• Incorporate attachment contents into issue context for processing
• Enhance issue handling with additional context from file attachments

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