add loader section component

Signed-off-by: Tobias Erbshäußer <tobias@tesoft.dev>

frontend/src/components/loader-section.njk

@@ -0,0 +1,37 @@
+<template id="tesoft-loader-section-template">
+    <style>
+        @import "/src/styles/default.css";
+
+        :host {
+            display: grid;
+        }
+
+        :host > div {
+            align-items: center;
+            display: grid;
+            grid-template-columns: 1fr;
+            grid-template-rows: 1fr;
+            justify-items: center;
+        }
+
+        :host([loaded]) > div {
+            align-self: start;
+        }
+
+        :host(:not([loaded])) slot {
+            display: none;
+        }
+
+        :host([loaded]) tesoft-loader {
+            display: none;
+        }
+    </style>
+
+    <div>
+        <tesoft-loader></tesoft-loader>
+        <slot></slot>
+    </div>
+</template>
+
+<script src="/src/components/loader-section.ts" type="module"></script>
+{% includeOnce 'components/loader.njk' %}

frontend/src/components/loader-section.ts

@@ -0,0 +1,23 @@
+import {TesoftComponent} from "../scripts/main.ts";
+
+export class TesoftLoaderSection extends TesoftComponent {
+    constructor() {
+        super();
+
+        const template = document.getElementById("tesoft-loader-section-template") as HTMLTemplateElement;
+        const templateContent = template.content;
+
+        const shadowRoot = this.attachShadow({mode: "open"});
+        shadowRoot.appendChild(templateContent.cloneNode(true));
+    }
+
+    reset() {
+        this.removeAttribute("loaded");
+    }
+
+    finish() {
+        this.setAttribute("loaded", "");
+    }
+}
+
+customElements.define("tesoft-loader-section", TesoftLoaderSection);