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/js/create_nx_workspace.go

@@ -1,14 +1,14 @@
 package js
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "create-nx-workspace",
 		Description: "The name of the workspace",
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--name", Description: "Workspace name (e.g., org name)"},
 			{Name: "--preset", Description: "Empty [an empty workspace with a layout that works best for building apps]"},
 			{Name: "--appName", Description: "The name of the application created by some presets"},