Ability to open a onenote section file from a buffer (slice)

[micahsnyder]

I would like the ability to open a OneNote section file from an in memory buffer such a slice of u8's.

For context, my project is a malware scanner that recursively extracts files and scans the content. Our scanner typically opens the file to access the contents before parsing with various parsers. I'm working on adding support for extracting attachments from OneNote sections and leveraging your library for handling newer style OneNote section files.

I have a PoC working and will submit a PR in a moment.

[micahsnyder]

@msiemens friendly ping.