tidb-in-kubernetes: add dind file back (#1322)
tidb-in-kubernetes: add dind file back (#1322)

* Revert "tidb-in-kubernetes: delete dind file (#1318)"

This reverts commit 5924f6ea86b91df1624c7ed236e0ecdcd21cb5e7.

* update code blocks

pingcap/docs,pingcap/docs,pingcap/docs