Add Waybar time tracker with README, styles, and config

Includes a dependency-free Python CLI, Waybar JSON output, persistent
JSON storage, and Markdown timesheet generation grouped by project and
day. Also adds example Waybar configuration and CSS.

style.css

@@ -0,0 +1,17 @@
+/* Waybar CSS for the time tracker module */
+#custom-timetrack {
+    padding: 0 12px;
+    border-radius: 4px;
+    margin: 4px 2px;
+    font-weight: bold;
+}
+
+#custom-timetrack.idle {
+    background-color: #3b3b3b;
+    color: #a0a0a0;
+}
+
+#custom-timetrack.running {
+    background-color: #2e7d32;
+    color: #ffffff;
+}