Refactoring: move all code files into a src directory

src/UI/Base/IfNot.svelte

@@ -0,0 +1,20 @@
+<script lang="ts">
+  import { UIEventSource } from "../../Logic/UIEventSource"
+  import { onDestroy } from "svelte"
+
+  /**
+   * For some stupid reason, it is very hard to let {#if} work together with UIEventSources, so we wrap then here
+   */
+  export let condition: UIEventSource<boolean>
+  let _c = !condition.data
+  onDestroy(
+    condition.addCallback((c) => {
+      _c = !c
+      return false
+    })
+  )
+</script>
+
+{#if _c}
+  <slot />
+{/if}