Restore “Restore Defaults” button in syntax editor

CotEditor/Sources/SyntaxEditView.swift

@@ -157,6 +157,11 @@ struct SyntaxEditView: View {
                 Divider()
                 
                 HStack {
+                    if self.isBundled {
+                        Button(String(localized: "Restore Defaults", table: "SyntaxEdit")) {
+                            self.restore()
+                        }.fixedSize()
+                    }
                     Spacer()
                     SubmitButtonGroup(action: self.submit) {
                         self.parent?.dismiss(nil)
@@ -243,6 +248,19 @@ struct SyntaxEditView: View {
     }
     
     
+    /// Restores the current settings in editor to the user default.
+    private func restore() {
+        
+        guard
+            self.isBundled,
+            let definition = SyntaxManager.shared.bundledDefinition(name: self.name)
+        else { return }
+        
+        self.syntax.update(with: definition)
+        self.errors = self.syntax.validate()
+    }
+    
+    
     /// Validates the passed-in syntax name.
     ///
     /// - Parameter name: The syntax name to test.

CotEditor/mul.lproj/SyntaxEdit.xcstrings

@@ -2973,6 +2973,76 @@
         }
       }
     },
+    "Restore Defaults" : {
+      "localizations" : {
+        "cs" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Výchozí hodnoty"
+          }
+        },
+        "de" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Standard wiederherstellen"
+          }
+        },
+        "en-GB" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Restore Defaults"
+          }
+        },
+        "es" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Restaurar valores por omisión"
+          }
+        },
+        "fr" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Réglages par défaut"
+          }
+        },
+        "it" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Ripristina default"
+          }
+        },
+        "ja" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "デフォルトに戻す"
+          }
+        },
+        "pt" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Restaurar Padrões"
+          }
+        },
+        "tr" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Saptanmışlara Dön"
+          }
+        },
+        "zh-Hans" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "恢复默认"
+          }
+        },
+        "zh-Hant" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "回復預設值"
+          }
+        }
+      }
+    },
     "Syntax.key.attributes.label" : {
       "comment" : "syntax highlight type",
       "extractionState" : "extracted_with_value",