This content-type is neccessary apparently: https://developer.mozilla.org/en/Apps/The_Manifest
To ensure the dir exists with git, a file is required - but it can be completely empty. Since the git ignore file is already in the repo it is not necessary to not-ignore it - it is already tracked. Though trivial these !.gitignore files are being understood by some to mean that they must contain this exact syntax to ensure an empty folder exists.
… opera extensions. Fixes #827