[functions] Repository setup

[dackers86]

Set up the Dart Firebase Functions SDK repository with proper infrastructure including:

• Continuous Integration / Continuous Development (CI/CD) pipelines
• GitHub Actions workflows
• Scripting and automation tools
• Code quality tooling (linting, formatting)

This establishes the foundational infrastructure for the Functions SDK development.

Dependencies: None

Acceptance Criteria:

• Repository created and configured
• CI/CD pipelines configured and working
• GitHub Actions workflows set up
• Linting and formatting tools configured
• README.md with setup instructions added