Add Giselle to repositories.toml

[masutaka]

trafficstars

ℹ️ Repository information

The repository has:

• [x] At least three issues with the good first issue label.
  • https://github.com/giselles-ai/giselle/issues?q=is%3Aissue%20state%3Aopen%20label%3A%22good%20first%20issue%22
• [x] At least 10 contributors.
  • https://github.com/giselles-ai/giselle/graphs/contributors
• [x] Detailed setup instructions for the project.
• [x] CONTRIBUTING.md
  • https://github.com/giselles-ai/giselle/blob/main/CONTRIBUTING.md
• [x] Actively maintained.