Update captions page

in-app-manual/captions.md

@@ -27,3 +27,5 @@ These files need to be named as follows:
 Where `{language_code}` is defined by the [ISO-6399-1](https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes){:target="_blank"} (2 letters) standard and `ext` is the file extension. Captions files without a language code will be labeled as Unknown in the video player but will work fine.
 
 Scenes with captions can be filtered with the `captions` criterion.
+
+**Note:** If the caption file was added after the scene was initially added during scan you will need to run a Selective Scan task for it to show up.