ADD: controller about search items by keyword

+package controller
+
+import (
+	"joongna/service"
+	"net/http"
+
+	"github.com/labstack/echo/v4"
+)
+
+func Search(c echo.Context) error {
+	keyword := c.Param("keyword")
+	items, err := service.GetItemByKeyword(keyword)
+	if err != nil {
+		return err
+	}
+	return c.JSON(http.StatusOK, items)
+}

 package router
 
-import "github.com/labstack/echo/v4"
+import (
+	"joongna/controller"
+
+	"github.com/labstack/echo/v4"
+)
 
 const (
 	API        = "/api/v2"