ci: Create dependabot.yml

[YDX-2147483647]

现在的CI有几十个warnings，大多是要求升级 Node.js 版本，只要更新即可解决。

相关文档：

• GitHub Actions: Transitioning from Node 16 to Node 20 - The GitHub Blog

  Our plan is to transition all actions to run on Node 20 by Spring 2024.

• Configuration options for the dependabot.yml file - GitHub Docs

• Deprecation notice: v3 of the artifact actions - The GitHub Blog

  The deprecation of v3…, which is scheduled to take place on June 30, 2024. …, attempting to use a version of the actions after the deprecation date will result in a workflow failure.

[fky2015]

dependabot 还能管 CI 里面依赖的 nodejs 嘛？

[YDX-2147483647]

唔，各个action的作者会管自己用的 Node.js 版本，然后dependabot（package-ecosystem: github-actions）会升级action版本。