docs: Add instructions for building with version info to CONTRIBUTING.md

[DylanDevelops]

Added a section to CONTRIBUTING.md explaining how to build the project with version information injected using Go build flags. This helps contributors test version display and verify version injection locally.

Pull Request Checklist

• I have read and followed the contribution guidelines.
• My pull request targets the main branch of tmpo.
• I have tested these changes locally on my machine.

Description

This pull request adds documentation to the CONTRIBUTING.md file explaining how to build the project with custom version information injected. This guidance is helpful for developers who want to test the version display or verify version injection locally.

Documentation improvements:

• Added a new section to CONTRIBUTING.md that details how to use go build with -ldflags to inject custom version, commit, and date information into the binary for local testing and verification.

Screenshots