implement enum for types, implement OpenDialog from Dialog-API

ElectronNET.API/Entities/DefaultFontFamily.cs

@@ -0,0 +1,35 @@
+namespace ElectronNET.API.Entities
+{
+    public class DefaultFontFamily
+    {
+        /// <summary>
+        /// Defaults to Times New Roman.
+        /// </summary>
+        public string Standard { get; set; }
+
+        /// <summary>
+        /// Defaults to Times New Roman.
+        /// </summary>
+        public string Serif { get; set; }
+
+        /// <summary>
+        /// Defaults to Arial.
+        /// </summary>
+        public string SansSerif { get; set; }
+
+        /// <summary>
+        /// Defaults to Courier New.
+        /// </summary>
+        public string Monospace { get; set; }
+
+        /// <summary>
+        /// Defaults to Script.
+        /// </summary>
+        public string Cursive { get; set; }
+
+        /// <summary>
+        /// Defaults to Impact.
+        /// </summary>
+        public string Fantasy { get; set; }
+    }
+}