Merge #620: Add demo warning banner

562dd29 fix: [#621] using a linked package isntead of NPM regsitry (Jose Celano)
92a3d48 feat: [#619] add demo warning banner (Jose Celano)

Pull request description:

  Add demo warning banner. The text can be overridden in the Index configuration:

  ```
  [website.demo]
  warning = """
  ⚠️ Please be aware: This demo resets all data weekly. Torrents not complying with our Usage Policies will be removed immediately without notice. We encourage the responsible use of this software in compliance with all legal requirements.
  """
  ```

  See torrust/torrust-index#730

ACKs for top commit:
  josecelano:
    ACK 562dd29

Tree-SHA512: 113c59e13dc5537f96dea3dac21fbae6f0ecc663c1d451db90f8c300c774e5c6f2868da191d4094ce229573b499ce9619df94e5f791da3ac047a4f3311542a8f

Author: josecelano

app.vue

@@ -1,5 +1,7 @@
 <template>
   <div class="flex flex-col" style="min-height: 100vh;">
+    <DemoBanner />
+
     <Notifications />
 
     <NavigationBar />
@@ -21,6 +23,7 @@
 <script setup lang="ts">
 import { getCategories, getSettings, getTags, getUser, onBeforeMount, onMounted } from "#imports";
 import Notifications from "~/components/Notifications.vue";
+import DemoBanner from "~/components/demo/Banner.vue";
 
 onBeforeMount(() => {
   getUser();

components/demo/Banner.vue

@@ -0,0 +1,44 @@
+<template>
+  <div v-if="isDemoMode" class="demo-banner">
+    {{ warning }}<NuxtLink to="/terms">
+      Read our terms.</NuxtLink>
+  </div>
+</template>
+
+<script setup lang="ts">
+import { type PublicSettings } from "torrust-index-types-lib";
+
+const settings = useSettings();
+const isDemoMode = ref(false);
+const warning = ref("");
+
+onMounted(() => {
+  isDemoMode.value = false;
+});
+
+watch(
+  () => settings.value,
+  (newSettings) => {
+    if (newSettings?.website?.demo?.warning) {
+      isDemoMode.value = true;
+      warning.value = newSettings?.website?.demo?.warning;
+    }
+  },
+  { immediate: true }
+);
+
+</script>
+
+<style scoped>
+.demo-banner {
+  background-color: #f5b14a;
+  color: #000;
+  width: 100%;
+  padding: 10px;
+  text-align: center;
+  /*position: fixed;*/
+  top: 0;
+  left: 0;
+  z-index: 1000;
+}
+</style>