Implement Fetch and FilterFetch derive macros

Author: vladbat00

Cargo.toml

@@ -270,6 +270,10 @@ path = "examples/ecs/component_change_detection.rs"
 name = "event"
 path = "examples/ecs/event.rs"
 
+[[example]]
+name = "fetch"
+path = "examples/ecs/fetch.rs"
+
 [[example]]
 name = "fixed_timestep"
 path = "examples/ecs/fixed_timestep.rs"