put shell in subdir, and add nix package

shell/bar/Clock.qml

@@ -0,0 +1,21 @@
+import QtQuick
+import Quickshell
+
+Text {
+    property string ap: sysClock.hours >= 12 ? "PM" : "AM"
+    property string minutes: sysClock.minutes.toString().padStart(2, '0')
+    property string hours: {
+        var value = sysClock.hours % 12;
+        if (value === 0)
+            return 12;
+        return value;
+    }
+
+    SystemClock {
+        id: sysClock
+        enabled: true
+    }
+
+    text: `${hours}:${minutes} ${ap}`
+    font.pointSize: 11
+}