Adding a global error message

This error message should be used for non fatal errors (otherwise, use the ErrorScene).
It is implemented using Svelte and the new "$errorStore".

Use `errorStore.addErrorMessage` to display the error popup with the message.

This PR uses this error message to display a popup explaining the browser is too old for WebRTC.

front/src/Components/App.svelte

@@ -9,6 +9,7 @@
     import {selectCharacterSceneVisibleStore} from "../Stores/SelectCharacterStore";
     import SelectCharacterScene from "./selectCharacter/SelectCharacterScene.svelte";
     import {customCharacterSceneVisibleStore} from "../Stores/CustomCharacterStore";
+    import {errorStore} from "../Stores/ErrorStore";
     import CustomCharacterScene from "./CustomCharacterScene/CustomCharacterScene.svelte";
     import LoginScene from "./Login/LoginScene.svelte";
     import {loginSceneVisibleStore} from "../Stores/LoginSceneStore";
@@ -21,6 +22,7 @@
     import HelpCameraSettingsPopup from "./HelpCameraSettings/HelpCameraSettingsPopup.svelte";
     import AudioPlaying from "./UI/AudioPlaying.svelte";
     import {soundPlayingStore} from "../Stores/SoundPlayingStore";
+    import ErrorDialog from "./UI/ErrorDialog.svelte";
 
     export let game: Game;
 </script>
@@ -78,4 +80,9 @@
     {#if $requestVisitCardsStore}
         <VisitCard visitCardUrl={$requestVisitCardsStore}></VisitCard>
     {/if}
+    {#if $errorStore.length > 0}
+    <div>
+        <ErrorDialog></ErrorDialog>
+    </div>
+    {/if}
 </div>

front/src/Components/UI/ErrorDialog.svelte

@@ -0,0 +1,44 @@
+<script lang="ts">
+import {errorStore} from "../../Stores/ErrorStore";
+
+function close(): boolean {
+    errorStore.clearMessages();
+    return false;
+}
+
+</script>
+
+<dialog class="error-dialog nes-dialog is-dark is-rounded" id="dialog-dark-rounded" open>
+    <p class="nes-text is-error title">Error</p>
+    <div class="body">
+    {#each $errorStore as error}
+    <p>{error}</p>
+    {/each}
+    </div>
+    <div class="button-bar">
+        <button class="nes-btn is-error" on:click={close}>Close</button>
+    </div>
+</dialog>
+
+<style lang="scss">
+    dialog.error-dialog {
+      pointer-events: auto;
+      top: 10%;
+
+      .button-bar {
+        text-align: center;
+      }
+
+      .body {
+        max-height: 50vh;
+      }
+
+      p {
+        font-family: "Press Start 2P";
+
+        &.title {
+          text-align: center;
+        }
+      }
+    }
+</style>