fix: apply --required-only to data directories

The Required packs and manifests carried every data tree, the FreeIntv
overlays included. A data_directories entry now accepts required: false,
and the platform, emulator and manifest walks leave such a tree out under
--required-only. FreeIntv reads its overlays only with the multi-screen
option and draws a placeholder keypad without one (src/libretro.c:294-296,
350-369).

scripts/scraper/libretro_scraper.py

@@ -495,8 +495,15 @@ class Scraper(BaseScraper):
             # so final path is system/freeintv_overlays/FreeIntvTS_Overlays/<rom>.png
             # but core expects system/freeintv_overlays/<rom>.png
             # fix: point destination into the subfolder
+            # Optional: read only with the multi-screen option on, and a
+            # missing PNG falls back to a drawn placeholder keypad
+            # (FreeIntv/src/libretro.c:294-296, 350-369).
             "mattel-intellivision": [
-                {"ref": "freeintv-overlays", "destination": "freeintv_overlays"},
+                {
+                    "ref": "freeintv-overlays",
+                    "destination": "freeintv_overlays",
+                    "required": False,
+                },
             ],
         }
         for sys_id, data_dirs in SYSTEM_DATA_DIRS.items():