Include Dash in GitHub Marketplace

[aalbuerne]

Description

Publish Dash in the GitHub Marketplace to make it easier for developers to discover and integrate it directly into their GitHub workflows. This includes preparing a GitHub App (if needed), configuring metadata, and setting up the install experience.

Why is this important?

• Visibility: being in the Marketplace increases exposure among GitHub users.
• Developer experience: simplifies onboarding and setup for new users.
• Integration: enables direct connection to repositories, pull requests, and workflows.
• Trust: GitHub Marketplace listings provide credibility and transparency.