docs: add Depot CI to continuous integration providers list

Made-with: Cursor

Author: ischolten

content/container-builds/how-to-guides/continuous-integration.mdx

@@ -20,6 +20,7 @@ Running `depot` in a continuous integration environment is a great way to get fa
 - [Bitbucket Pipelines](/docs/container-builds/integrations/bitbucket-pipelines)
 - [Buildkite](/docs/container-builds/integrations/buildkite)
 - [CircleCI](/docs/container-builds/integrations/circleci)
+- [Depot CI](/docs/ci/quickstart)
 - [GitHub Actions](/docs/container-builds/integrations/github-actions)
 - [GitLab CI](/docs/container-builds/integrations/gitlab-ci)
 - [Google Cloud Build](/docs/container-builds/integrations/google-cloud-build)