Function read_file_from_fs 

pub fn read_file_from_fs(file_path: &Path) -> Result<EmbeddedFile>

Reads a file from the file system and computes its metadata.

file_path is expected to be an absolute, canonical path inside the assets folder. The hash of the file is cached and only recomputed when the file’s length or modification time changed. Returns an io::Error when the file cannot be opened or read.