Sync eng/common directory with azure-sdk-tools for PR 1178 (#13412)
Sync eng/common directory with azure-sdk-tools for PR 1178 (#13412)

* Refactor eng/common/README.md

* Add doc directory

Co-authored-by: Chidozie Ononiwu <301d19fba573b360a93464351d7ca3ed97357016@microsoft.com>
Azure/azure-sdk-for-go,Azure/azure-sdk-for-go,Azure/azure-sdk-for-go,Azure/azure-sdk-for-go