Add BasicLocalSavegames (basic_feature) (#122)

* Add `basic_feature.BasicLocalSavegames`
(profile specific save games)

* Refactor Black & White 2 with BasicLocalSavegames

* Refactor Valheim with BasicLocalSavegames

* Refactor Vampire Bloodlines with BasicLocalSavegames

* Add info about basic local save games to readme

basic_features/basic_local_savegames.py

@@ -0,0 +1,21 @@
+import mobase
+from PyQt6.QtCore import QDir
+
+
+class BasicLocalSavegames(mobase.LocalSavegames):
+    def __init__(self, game_save_dir: QDir):
+        super().__init__()
+        self._game_saves_dir = game_save_dir.absolutePath()
+
+    def mappings(self, profile_save_dir: QDir):
+        return [
+            mobase.Mapping(
+                source=profile_save_dir.absolutePath(),
+                destination=self._game_saves_dir,
+                is_directory=True,
+                create_target=True,
+            )
+        ]
+
+    def prepareProfile(self, profile: mobase.IProfile) -> bool:
+        return profile.localSavesEnabled()