chore: delete the footer component (according to review)

pls refer to !215 (comment 375185)

src/components/footer.vue

-<template>
-  <q-toolbar
-    :class="$q.dark.isActive ? 'bg-dark' : 'bg-secondary text-primary'"
-  >
-    <div class="footer__wrap">
-      <div
-        bordered
-        class="row justify-center items-center"
-        reveal
-      >
-        <Language v-if="config['language-switch']" />
-
-        <Color :projectcolors="projectcolors" />
-        <Softwareinfo />
-      </div>
-    </div>
-  </q-toolbar>
-</template>
-
-<script>
-import Color from '@/components/color.vue';
-import Language from '@/components/language.vue';
-import Softwareinfo from '@/components/softwareinfo.vue';
-
-export default {
-  name: 'Footer',
-  components: {
-    Color,
-    Language,
-    Softwareinfo,
-  },
-  props: {
-    config: {
-      type: Object,
-      default: () => {},
-    },
-    projectcolors: {
-      type: Object,
-      default: () => {},
-    },
-
-  },
-};
-</script>
-
-<style lang="scss" scoped>
-.footer__wrap {
-  margin: 0 auto;
-  max-width: 1200px;
-}
-</style>

src/index.template.html

@@ -83,7 +83,7 @@
         "item": "Sheet",
         "manifest": "Manuscript"
       },
-      "lang": "de-de",
+      "lang": "en-us",
       "language-switch": true,
       "meta": {
         "collection": {