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.

waybar-config.json

@@ -0,0 +1,12 @@
+{
+  "modules-center": ["custom/timetrack"],
+  "custom/timetrack": {
+    "exec": "/home/fegger/Code/projects/time_track/time_track.py status",
+    "interval": 5,
+    "format": "{}",
+    "return-type": "json",
+    "on-click": "/home/fegger/Code/projects/time_track/time_track.py toggle",
+    "on-click-right": "/home/fegger/Code/projects/time_track/time_track.py timesheet week",
+    "tooltip": true
+  }
+}