Dependabot deno support for version updates [GA]

### Value Prop
Teams building with Deno can now keep their dependencies up to date automatically through Dependabot version updates—without leaving GitHub. Deno's adoption continues to grow, and developers using it deserve the same first-class dependency management experience that npm, pip, and other ecosystems already enjoy. By extending Dependabot to support Deno, we remove a manual maintenance burden and help customers stay secure and current with minimal effort.

### Expected Outcome
With this release, Dependabot will automatically detect outdated dependencies in Deno projects and open pull requests to update them. We expect this to reduce the time developers spend manually tracking and updating Deno dependencies, increase the share of Deno projects with up-to-date dependency graphs, and close a gap that has driven customer feedback requesting parity with other supported ecosystems. This is available on GitHub.com (Free, Teams, and Enterprise plans) and GitHub Enterprise Server 3.22+.

此路线图 issue 描述了面向 Deno 项目的 Dependabot 版本更新计划中的 GA 功能，但没有列出任何仓库文件、测试或实现入口。首先定位负责生态系统版本更新及其 Deno 支持的 Dependabot 组件，然后围绕检测过时的 Deno 依赖项和创建更新 pull request 定义验证。

由索引模型根据 Issue 内容生成。