Rewrite index page in svelte, rewrite language picker in Svelte, fix #1612

src/UI/Base/Dropdown.svelte

@@ -1,14 +1,31 @@
 <script lang="ts">
-  import { UIEventSource } from "../../Logic/UIEventSource.js"
+  import { UIEventSource } from "../../Logic/UIEventSource.js";
 
-  /**
-   * For some stupid reason, it is very hard to bind inputs
-   */
-  export let value: UIEventSource<number>
-  let i: number = value.data
-  $: value.setData(i)
+  export let value: UIEventSource<any>
+  let i: any = value.data
+  let htmlElement : HTMLSelectElement
+  function selectAppropriateValue(){
+    if(!htmlElement){
+      return;
+    }
+    const v = value.data
+    for (let option of htmlElement.getElementsByTagName("option")) {
+      if(option.value === v){
+        option.selected = true
+        return
+      }
+    }
+  }
+  
+  
+  value.addCallbackD(() => selectAppropriateValue())
+  $: {
+    if(htmlElement){
+      selectAppropriateValue()
+    }
+  }
 </script>
 
-<select bind:value={i}>
+<select bind:this={htmlElement} on:change={(e) => {value.setData(e.srcElement.value)}}>
   <slot />
 </select>