add / check support for ext4 features

[joachimmetz]

ext4 features

• flex and meta block group - add support for flex and meta block groups #12
• codepage - add support for codepage #11
• add 64-bit inode support
• add support for sparse superblock v2
• complete metadata checksum support
• add orphan list and orphan file support
• add huge file inode support
• ext4 case folding (case insensitive) - https://lwn.net/Articles/784041/
• other flags that might be good to be strict with?
• Verity protected inode - https://www.kernel.org/doc/html/latest/filesystems/fsverity.html