Add github label integration

[Djiit]

This issue is to add a GitHub label integration to gong.

Overview

The GitHub label integration should allow automatically applying/removing labels to PRs based on reviewer response time.

Implementation Details

1. Create a new package in internal/integrations/githublabel
2. Implement the label integration interface
3. Add support for configurable label names and application rules
4. Add configuration parameters for GitHub label operations

Acceptance Criteria

• GitHub labels can be applied or removed based on review status
• Label operations can be configured globally or per rule
• The integration can be used alongside other integrations (Slack, Comment, etc.)
• The integration is properly documented in the docs
• Unit tests are written for the implementation
• Update examples in configuration documentation

References

See existing integrations for good examples to follow. This integration will need to use the GitHub API to apply/remove labels.

Labels: integration, help wanted