Fix debugability of non-existent plugins or variables in non-production mode

.vscode/settings.json

@@ -19,6 +19,7 @@
         "stefanfritsch",
         "Strikethrough",
         "tasklist",
+        "Texter",
         "wikilink",
         "yuin",
         "ZSCONFIG",

main.go

@@ -455,6 +455,10 @@ func render(s string, vars Vars) (string, error) {
 			} else {
 				log.WithError(err).Warnf("error running command: %s", m[0])
 			}
+		} else {
+			if !viper.GetBool("production") {
+				out.WriteString(fmt.Sprintf("%s: plugin or variable not found", m[0]))
+			}
 		}
 	}