[bunkr] update default archive ID format (#6935)

use 'name' when there is no proper 'id' value available.

gallery_dl/extractor/bunkr.py

@@ -60,6 +60,7 @@ class BunkrAlbumExtractor(LolisafeAlbumExtractor):
     """Extractor for bunkr.si albums"""
     category = "bunkr"
     root = "https://bunkr.si"
+    archive_fmt = "{album_id}_{id|name}"
     pattern = BASE_PATTERN + r"/a/([^/?#]+)"
     example = "https://bunkr.si/a/ID"