Browsing Serbian translation

note: 'Open label.'
note: 'The text in the keyboard overlay to explain the shortcut (open a file).'
note: 'The text of the button to open Apps Developer Tools in the banner to invite people to use Apps Developer Tools.'
note: 'Title of the action for installing extension from CRX file.'
note: 'Title of the action for mounting an archive file to work with its contents.'
in: upstream/cr-28.0.1500.95/chrome/app/chromeos_strings.grdp, as IDS_KEYBOARD_OVERLAY_OPEN
in: upstream/cr-28.0.1500.95/chrome/app/generated_resources.grd, as IDS_FILE_BROWSER_MOUNT_ARCHIVE