Add dark theme

app/src/main/java/com/annimon/hotarufx/Main.java

@@ -18,6 +18,11 @@ public class Main extends Application {
         try {
             val loader = new FXMLLoader(getClass().getResource("/fxml/Editor.fxml"));
             val scene = new Scene(loader.load());
+            scene.getStylesheets().addAll(
+                    getClass().getResource("/styles/theme-dark.css").toExternalForm(),
+                    getClass().getResource("/styles/codearea.css").toExternalForm(),
+                    getClass().getResource("/styles/hotarufx-keywords.css").toExternalForm()
+                    );
             controller = loader.getController();
             primaryStage.setScene(scene);
         } catch (IOException e) {

app/src/main/resources/styles/codearea.css

@@ -0,0 +1,16 @@
+.styled-text-area {
+    -fx-background-color: #383838;
+    -fx-highlight-fill: #A7A047;
+}
+.text {
+    -fx-fill: #dadada;
+}
+.caret {
+    -fx-stroke: #F2E52B;
+}
+.lineno {
+    -fx-background-color: #2f2f2f;
+    -fx-font-size: 0.8em;
+    -fx-text-fill: #505050;
+    //-fx-opacity: 0.8;
+}

app/src/main/resources/styles/hotarufx-keywords.css

@@ -0,0 +1,15 @@
+.keyword {
+    -fx-fill: #A648FF;
+}
+.comment {
+	-fx-fill: #969696;
+}
+.string {
+	-fx-fill: #F89722;
+}
+.number {
+	-fx-fill: #8DB8C7;
+}
+.node-function {
+	-fx-fill: #1899C7;
+}

app/src/main/resources/styles/theme-dark.css

@@ -0,0 +1,45 @@
+.root {
+    -fx-base: #2F2F2F;
+    -fx-background: -fx-base;
+    -fx-accent: #CFC539;
+
+    -fx-color: derive(-fx-base, 10%);
+
+    -fx-control-inner-background: derive(-fx-base, 5%);
+    -fx-control-inner-background-alt: derive(-fx-control-inner-background, 2%);
+
+    -fx-light-text-color: #CCCCCC;
+    -fx-mid-text-color: #505050;
+    -fx-dark-text-color: #050505;
+    -fx-focus-color: -fx-accent;
+}
+
+/* Menu */
+.menu-bar {
+    -fx-background-color: -fx-base;
+}
+.menu-bar > .container > .menu-button:hover > .label,
+.menu-bar > .container > .menu-button:focused > .label,
+.menu-bar > .container > .menu-button:showing > .label {
+    -fx-text-fill: #FFFFFF;
+}
+.menu-item:focused {
+    -fx-background-color: #4E5052;
+}
+.menu-item:focused > .label {
+    -fx-text-fill: -fx-light-text-color;
+}
+
+/* Scroll-bar */
+.scroll-bar > .thumb {
+    -fx-color: derive(-fx-accent, -50%);
+}
+.scroll-bar > .thumb:hover,
+.scroll-bar > .increment-button:hover,
+.scroll-bar > .decrement-button:hover {
+    -fx-color: -fx-accent;
+}
+.scroll-bar > .increment-button > .increment-arrow,
+.scroll-bar > .decrement-button > .decrement-arrow {
+    -fx-background-color: derive(-fx-accent, -20%);
+}