Common subcommand naming scheme (#208)

drop tea mile alias

document command schema in CONTRIBUTING.md

and update this file, its a plain copy from gitea

add "list" as alias for "ls" subcommand

add singular command aliases

Co-authored-by: Norwin Roosen <git@nroo.de>
Reviewed-on: https://gitea.com/gitea/tea/pulls/208
Reviewed-by: 6543 <6543@noreply.gitea.io>
Reviewed-by: techknowlogick <techknowlogick@gitea.io>

cmd/labels.go

@@ -23,6 +23,7 @@ import (
 // CmdLabels represents to operate repositories' labels.
 var CmdLabels = cli.Command{
 	Name:        "labels",
+	Aliases:     []string{"label"},
 	Usage:       "Manage issue labels",
 	Description: `Manage issue labels`,
 	Action:      runLabels,