Macro plugin

macro_rules! plugin {
    (
        id: $id:expr,
        name: $name:expr,
        version: $version:expr,
        author: $author:expr,
        description: $description:expr,
        $(license: $license:expr,)?
        $(permissions: [$($permission:expr),*],)?
        $(dependencies: [$($dep:expr),*],)?
        impl $impl_block:tt
    ) => { ... };
    (@license) => { ... };
    (@license $license:expr) => { ... };
}

Create a plugin with basic metadata using a more ergonomic syntax