Implement damage UI, damage and stale moves. (#45)

Reviewed-on: #45
Co-authored-by: Álex Román Núñez <eirexe@eirteam.moe>

src/ui/errors.rs

@@ -0,0 +1,14 @@
+use bevy::{scene::SpawnSceneError};
+
+use crate::{fighter::FighterId};
+
+#[derive(thiserror::Error, Debug)]
+pub enum UIErrors {
+    #[error("Scene spawn failed: {0:?}")]
+    SceneSpawnFailed(#[from] SpawnSceneError),
+    #[error("Fighter manifest handle not found for fighter id {0:?}")]
+    FighterManifestHandleNotFound(FighterId),
+
+    #[error("Fighter manifest not found for fighter id {0:?}")]
+    FighterManifestNotFound(FighterId),
+}