add Azure Pipelines badge to README (#6816)
add Azure Pipelines badge to README (#6816)

Description: adds an Azure Pipelines badge to the readme
Risk Level: low
Testing: n/a
Docs Changes: n/a
Release Notes: n/a

Signed-off-by: Matt Cooper <5c60167fcca33e0157564107b74ca4e571304e39@xbox.com>
eklitzke/envoy,lyft/envoy,envoyproxy/envoy-wasm,istio/envoy,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy,istio/envoy,jrajahalme/envoy,istio/envoy,envoyproxy/envoy,istio/envoy,lizan/envoy,lizan/envoy,envoyproxy/envoy,jrajahalme/envoy,lizan/envoy,envoyproxy/envoy,lyft/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy,jrajahalme/envoy,lizan/envoy,envoyproxy/envoy,lizan/envoy,envoyproxy/envoy,envoyproxy/envoy,eklitzke/envoy,lyft/envoy,istio/envoy,lizan/envoy,istio/envoy,envoyproxy/envoy-wasm,jrajahalme/envoy,jrajahalme/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy-wasm,lyft/envoy,eklitzke/envoy,envoyproxy/envoy-wasm,jrajahalme/envoy,eklitzke/envoy,lyft/envoy,istio/envoy,envoyproxy/envoy,lyft/envoy,eklitzke/envoy,eklitzke/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy