Fix caption in attached document sending messages (#2226)

* Caption for attached document

* Update Injected.js

---------

Co-authored-by: tuyuribr <45042245+tuyuribr@users.noreply.github.com>
Co-authored-by: Pedro S. Lopez <pedroslopez@me.com>

src/util/Injected.js

@@ -120,6 +120,9 @@ exports.LoadUtils = () => {
                     forceGif: options.sendVideoAsGif
                 });
             
+            if (options.caption){
+                attOptions.caption = options.caption; 
+            }
             content = options.sendMediaAsSticker ? undefined : attOptions.preview;
 
             delete options.attachment;