Add migrate command (#207)

* Add base and loader command

* Support updating to latest

* Support explicit fabric versions

* Support explicit Forge version

* Support quilt

* Add support for updating Minecraft

* Add support for Forge recommended

* Fix Forge version sorting

* Various fixes

* Add documentation to the use

* More suggestions

migrate/migrate.go

@@ -0,0 +1,16 @@
+package migrate
+
+import (
+	"github.com/packwiz/packwiz/cmd"
+	"github.com/spf13/cobra"
+)
+
+// migrateCmd represents the base command when called without any subcommands
+var migrateCmd = &cobra.Command{
+	Use:   "migrate [minecraft|loader]",
+	Short: "Migrate your Minecraft and loader versions to newer versions.",
+}
+
+func init() {
+	cmd.Add(migrateCmd)
+}