refactor(commands): separate commands and its core into two folders (#32)

- I think it would be better if one for commands only, one for the spec
handling core logic so people won't be confused by the core logic inside
the commands folder (cleaner I guess)
- Regen docs

commands/sys/tailcall.go

@@ -1,20 +1,20 @@
 package sys
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "tailcall",
 		Description: "TailCall CLI for managing and optimizing GraphQL configurations",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "check", Description: "Validate a composition spec"},
 			{Name: "start", Description: "Launch the GraphQL Server for the specific configuration"},
 			{Name: "init", Description: "Bootstrap a new TailCall project"},
 			{Name: "gen", Description: "Generate GraphQL configurations from various sources"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--n-plus-one-queries", Description: "Detect N+1 issues"},
 			{Name: "--schema", Description: "Display the schema of the composition spec"},
 			{Name: "--format", Description: "Change the format of the input file"},