message: add apk mime type
diff: @@ -62,6 +62,7 @@ static unordered_map<string, string> mime_map({
  { "jar", "application/java-archive" },
  { "war", "application/java-archive" },
  { "ear", "application/java-archive" },
  + { "apk", "application/vnd.android.package-archive" },
  { "ser", "application/java-serialized-object" },
  { "class", "application/java-vm" },
  { "js", "application/javascript" },
  