add missing copyright headers

crates/fayalite/src/sim.rs

@@ -1,3 +1,6 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
 //! Fayalite Simulation
 
 use crate::{

crates/fayalite/src/sim/interpreter.rs

@@ -1,3 +1,6 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
 use crate::{
     intern::{Intern, Interned},
     source_location::SourceLocation,