Update CONTRIBUTING.md to point to Community Guidelines
Update CONTRIBUTING.md to point to Community Guidelines

google-org/sandbox-detroit,google/opensmartbutton,googleinterns/app-action-visualizer,googleinterns/vm-network-migration,GoogleChromeLabs/lighthouse-bot-starter,googleinterns/smart-news-query-embeddings,bazelbuild/rules_fuzzing,google/chrome-tabber,googleinterns/voxetta,googleinterns/smart-news-query-embeddings,tensorflow/java-ndarray,google-org/sandbox-detroit,googleinterns/voxetta,GoogleChromeLabs/lighthouse-bot-starter,bazelbuild/rules_fuzzing,google/opensmartbutton,google/opensmartbutton,google/chrome-tabber,bazelbuild/rules_fuzzing,googleinterns/voxetta,google-org/sandbox-detroit