Add configuration for sharing emoji packs

This adds the configuration interface for the endpoints introduced here.

src/views/emoji-packs/components/EmojiPack.vue

@@ -18,6 +18,10 @@
       <el-input v-model="fallbackSrc" />
     </prop-editing-row>
 
+    <prop-editing-row v-if="fallbackSrc && fallbackSrc.trim() !== ''" name="Fallback source SHA">
+      {{ pack.pack["fallback-src-sha256"] }}
+    </prop-editing-row>
+
     <el-button type="success" @click="savePackMetadata">Save pack metadata</el-button>
 
     <el-collapse v-model="shownPackEmoji" class="contents-collapse">