Upgrading Github-Action to Leverage oasdiff-service

[effoeffi]

👋 We're planning a significant enhancement for our oasdiff-action, and we'd love your input.

Currently, our oasdiff-action involves 2 redundant calls to the oasdiff functionality, leading to inefficiencies. To streamline this, we aim to transition to the oasdiff-service, consolidating these calls into one for:

1. Generating github-action step output.
2. github-action annotation format output.
3. Adding Changelog and badge generation.

This upgrade is enabler for new features, including a hosted changelog and a version-badge with color indicators. Embrace efficiency and enhanced visibility with this optimized workflow 🚀

[bdoughan-snow]

Could annotation output be added to the OpenAPI document itself like the Spectral GitHub action does?