Move workspace crates into subfolder

crates/items_0/src/framable.rs

@@ -0,0 +1,19 @@
+// Required for any inner type of Sitemty.
+pub trait FrameTypeInnerStatic {
+    const FRAME_TYPE_ID: u32;
+}
+
+// To be implemented by the T of Sitemty<T>, e.g. ScalarEvents.
+pub trait FrameTypeInnerDyn {
+    // TODO check actual usage of this
+    fn frame_type_id(&self) -> u32;
+}
+
+impl<T> FrameTypeInnerDyn for T
+where
+    T: FrameTypeInnerStatic,
+{
+    fn frame_type_id(&self) -> u32 {
+        <Self as FrameTypeInnerStatic>::FRAME_TYPE_ID
+    }
+}