Add include paths to CompilerConfiguration

We'll try to load .60 files from those paths.

sixtyfps_compiler/diagnostics.rs

@@ -292,3 +292,11 @@ impl quote::ToTokens for BuildDiagnostics {
         self.iter().for_each(|diag| diag.to_tokens(tokens))
     }
 }
+
+impl Extend<FileDiagnostics> for BuildDiagnostics {
+    fn extend<T: IntoIterator<Item = FileDiagnostics>>(&mut self, iter: T) {
+        for diag in iter {
+            self.add(diag)
+        }
+    }
+}