Add new timeout option and supporting settings infrastructure

ntfysh_client/SettingsDialog.cs

@@ -0,0 +1,29 @@
+using System;
+using System.Windows.Forms;
+
+namespace ntfysh_client
+{
+    public partial class SettingsDialog : Form
+    {
+        public decimal Timeout
+        {
+            get => timeout.Value;
+            set => timeout.Value = value;
+        }
+
+        public SettingsDialog()
+        {
+            InitializeComponent();
+        }
+
+        private void saveButton_Click(object sender, EventArgs e)
+        {
+            DialogResult = DialogResult.OK;
+        }
+
+        private void cancelButton_Click(object sender, EventArgs e)
+        {
+            DialogResult = DialogResult.Cancel;
+        }
+    }
+}