security: blameless postmortem template. (#6553)
security: blameless postmortem template. (#6553)

Modified from
https://raw.githubusercontent.com/dastergon/postmortem-templates/master/templates/postmortem-template-srebook.md
and https://landing.google.com/sre/book/chapters/postmortem.html.

Signed-off-by: Harvey Tuch <c185081708e02336640916420d0c772668570de5@google.com>
istio/envoy,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy-wasm,dnoe/envoy,lyft/envoy,envoyproxy/envoy,lyft/envoy,istio/envoy,eklitzke/envoy,lizan/envoy,lizan/envoy,dnoe/envoy,lizan/envoy,jrajahalme/envoy,envoyproxy/envoy,envoyproxy/envoy-wasm,eklitzke/envoy,jrajahalme/envoy,istio/envoy,dnoe/envoy,envoyproxy/envoy,envoyproxy/envoy,istio/envoy,lizan/envoy,eklitzke/envoy,lyft/envoy,envoyproxy/envoy-wasm,istio/envoy,dnoe/envoy,lizan/envoy,lyft/envoy,jrajahalme/envoy,istio/envoy,envoyproxy/envoy,lizan/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy,istio/envoy,envoyproxy/envoy,eklitzke/envoy,dnoe/envoy,eklitzke/envoy,envoyproxy/envoy,jrajahalme/envoy,envoyproxy/envoy-wasm,jrajahalme/envoy,jrajahalme/envoy,envoyproxy/envoy-wasm,eklitzke/envoy,lyft/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy,envoyproxy/envoy,lyft/envoy