Refer to kubeedge/community as authoritative source for code of conduct

[Shelley-BaoYue]

There are multi copies of a code-of-conduct.md file scattered across repos in kubeedge. I'd like to change them to a redirect to the code-of-conduct.md file living in this repo as the authoritative source.

• community-infra
• killercoda-scenarios
• viaduct
• beehive
• examples
• edgemesh
• kubeedge
• ianvs
• sedna
• website
• mappers-go
• keink
• dashboard