add script to load dataset

README.md

@@ -66,7 +66,23 @@ Note that to perform the retrieval, it need to be used together with [castorini/
 }
 ```
 
-Citation Information
+# Load Dataset
+
+An example to load the dataset:
+```
+language = 'english'
+
+# to load all train, dev and test sets
+dataset = load_dataset('castorini/mr-tydi', language)
+
+# or to load a specific set:
+set_name = 'train'
+dataset = load_dataset('castorini/mr-tydi', language, set_name)
+```
+Note that the 'combined' option has only the 'train' set.
+
+
+# Citation Information
 ```
 @article{mrtydi,
       title={{Mr. TyDi}: A Multi-lingual Benchmark for Dense Retrieval},