Another parser for the VMF format, this time in Rust.
VMF is not a very complex format, so most of the API should be self-explanatory.
Perhaps the most interesting feature is the ability to "brin your own key": the
parser is agnostic over what type is used for the keys (block and property
names), as long as it implements From<&str>. This means you can use a good old
String, or a string_cache::Atom using
a static table pre-filled with some VMF-related keywords.