Add configuration for sharing emoji packs

This adds the configuration interface for the endpoints introduced here.

src/api/emoji_packs.js

@@ -70,6 +70,23 @@ export async function updatePackFile(host, token, args) {
   let data = null
 
   switch (args.action) {
+    case 'add': {
+      const { shortcode, file, fileName } = args
+
+      console.log(file)
+
+      data = fileUpdateFormData({
+        action: 'add',
+        shortcode: shortcode,
+        file: file
+      })
+      if (fileName.trim() !== '') {
+        data.set('filename', fileName)
+      }
+
+      break
+    }
+
     case 'update': {
       const { oldName, newName, newFilename } = args