Could include a full, step-by-step, `cargo vita` workflow

[workingjubilee]

See title, I guess?

I do mean from absolute zero to cargo vita vpk build --release, no partial instructions like "add this to your Cargo.toml, and hopefully that means your toml contains enough information to function now and no conflicting information". This is because it is very likely someone will find the documentation after considerable thrashing, so they may have put their dev environment into an erroneous state, or otherwise be confused and find it hard to understand even "clear" instructions. Something methodical and complete, with complete snapshots of relevant files, makes it easier to check themselves against the "right way".