Add an option to specify tabby encoding

This relies on a not-yet-merged patch to datalad-tabby, so we call
load_tabby without additional arguments unless the encoding is
given. If the patch gets merged, the if-else can be removed.

Related datalad-tabby change:
psychoinformatics-de/datalad-tabby#116

load_tabby.py

@@ -289,12 +289,20 @@ def process_homepage(homepage):
 parser.add_argument("-c", "--catalog", type=Path, help="Catalog to add to")
 parser.add_argument("--set-as-super", action="store_true")
 parser.add_argument("--remove-first", action="store_true")
+parser.add_argument("--encoding", help="encoding to use when loading tabby")
 args = parser.parse_args()
 
-record = load_tabby(
-    args.tabby_path,  # projects/project-a/example-record/[email protected]
-    cpaths=[Path(__file__).parent / "conventions"],
-)
+if args.encoding:
+    record = load_tabby(
+        args.tabby_path,
+        cpaths=[Path(__file__).parent / "conventions"],
+        encoding=args.encoding,
+    )
+else:
+    record = load_tabby(
+        args.tabby_path,
+        cpaths=[Path(__file__).parent / "conventions"],
+    )
 
 expanded = jsonld.expand(record)
 compacted = jsonld.compact(record, ctx=cat_context)