fixed error when alt is longer than 1500

app/mastodon_account.rb

···
     @config = File.exist?(CONFIG_FILE) ? YAML.load(File.read(CONFIG_FILE)) : {}
   end
 
+  def max_alt_length
+    1500
+  end
+
   def save_config
     File.write(CONFIG_FILE, YAML.dump(@config))
   end

app/tootify.rb

···
         cid = image['image']['ref']['$link']
         mime = image['image']['mimeType']
 
+        if alt.length > @mastodon.max_alt_length
+          alt = alt[[e-mail]_alt_length - 3] + "(…)"
+        end
+
         data = @bluesky.fetch_blob(cid)
 
         uploaded_media = @mastodon.upload_media(data, cid, mime, alt)