chore: complete Cargo.toml
feat: add copy_to and move_to functions
feat: add remove_flag function
chore: organize errors in error module
feat: add proper folder support
refactor: shorten parse_month function
refactor: restructure public API and add more docstrings
chore: rename "messages" methods to "entries"
chore: fix clippy lints
test: add checksum unit test
feat: parse datetime and use in human-centric part
docs: flesh out docstrings
feat: allow setting metadata for Entry
feat: implement delivery
feat: move m2store to own module and prepare deliver
feat: M2dir from path and move to separate module
style: add rustfmt.toml
refactor: separate out Entry into own module
feat: implement FromIterator<AsRef<Path>> for Metadata