Add validate to components (#1631)

Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>

esphome/loader.py

@@ -80,6 +80,10 @@ class ComponentManifest:
     def codeowners(self) -> List[str]:
         return getattr(self.module, "CODEOWNERS", [])
 
+    @property
+    def validate(self):
+        return getattr(self.module, "validate", None)
+
     @property
     def source_files(self) -> Dict[Path, SourceFile]:
         ret = {}