Right click or long press on a gallery photo now opens a menu to copy its permalink or share it.
The permalink id is the SHA-256 of the original photo file so it survives reordering and rebuilds.
Each photo also gets a small noindex share page carrying its own link preview image.
Fixed the entrypoint script being checked out with CRLF on Windows by adding a gitattributes file.
Reviewed-on: #36
