Improve 'slopes' input, add compass indicator

src/UI/Debug/OrientationDebugPanel.svelte

@@ -0,0 +1,22 @@
+<script lang="ts">
+  import { Orientation } from "../../Logic/Web/Orientation"
+
+  const o = Orientation.singleton
+  let alpha = o.alpha
+  let beta = o.beta
+  let gamma = o.gamma
+  let absolute = o.absolute
+  let gotMeasurement = o.gotMeasurement
+  o.startMeasurements()
+</script>
+{#if !$gotMeasurement}
+  No device orientation data available
+{:else}
+  Device orientation data:
+  <ol>
+    <li>Alpha: {$alpha}</li>
+    <li>Beta: {$beta}</li>
+    <li>Gamma: {$gamma}</li>
+    <li>Absolute?: {$absolute}</li>
+  </ol>
+{/if}