Add 'FromFen' trait

src/board/fen.rs

@@ -0,0 +1,6 @@
+/// A trait to mark items that can be converted from a FEN input.
+pub trait FromFen: Sized {
+    type Err;
+
+    fn from_fen(s: &str) -> Result<Self, Self::Err>;
+}

src/board/mod.rs

@@ -10,6 +10,9 @@ pub use color::*;
 pub mod direction;
 pub use direction::*;
 
+pub mod fen;
+pub use fen::*;
+
 pub mod file;
 pub use file::*;