feat(rc): store all clusters in a single kubeconfig with multiple contexts

fix: handle nil metadata fields in watchchanges

feat: auto set up config & simplify config file - directly use api.Cluster and api.AuthInfo

feat: add k import

feat: improve diff rendering

fix: remove gjson dependency (it's buggy) and update JSON parsing logic

fix: fix buffer size for scanner to handle larger inputs

rename env var; refactor code

rm unneeded code

add more options for visualizing diff

1st commit