Write some info in README.md, design titlebar, make downloader and very basic instance checker

res/css/main.css

@@ -0,0 +1,47 @@
+:root {
+	color: rgba(248, 248, 248, 1.0);
+}
+
+body {
+	margin: 0px;
+}
+
+#titlebar {
+	display: flex;
+	flex-direction: row;
+	justify-content: space-between;
+	align-items: center;
+	-webkit-app-region: drag;
+	width: 100%;
+	height: 24px;
+	position: absolute;
+	top: 0px;
+	left: 0px;
+	background-color: rgba(16, 16, 16, 1.0);
+}
+
+#window-actions {
+	display: flex;
+	flex-direction: row;
+	height: 100%;
+	-webkit-app-region: no-drag;
+	pointer-events: all;
+}
+
+.window-action {
+	background-color: rgba(24, 24, 32, 1.0);
+	width: 32px;
+	height: 100%;
+}
+
+.window-action:hover {
+	background-color: rgba(48, 48, 64, 1.0);
+}
+
+#window-close {
+	background-color: rgba(128, 0, 0, 1.0);
+}
+
+#window-close:hover {
+	background-color: rgba(248, 0, 0, 1.0);
+}