webview css: Fix sizing of message_inline_ref images.
webview css: Fix sizing of message_inline_ref images.

message_inline_ref images are mostly of preview of videos like dropbox
videos etc. Add same css as of twitter-image and message_inline_image.

This matches the webapp in applying this treatment to this same set of
three selectors.

vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile