Create integrations.md

[leotsarev]

Start docs for #692

1. How-to commit hook (from https://medium.com/@randulakoralage82/format-your-net-code-with-git-hooks-a0dc33f68048)
2. Azure Dev Ops sample (from my own https://github.com/joinrpg/joinrpg-net/blob/a60041e1fc361c4b1b71863696420348ac5a3e80/azure-pipelines.check.pr.yml)

[JoeRobich]

@leotsarev This is great. Could you add a line for each section to give credit to the original authors? Something like "These instructions originally authored by randulakoralage82."

[leotsarev]

@JoeRobich do I need to give credit to myself? :-)

[JoeRobich]

@leotsarev Thanks again!