Update map_fp2_to_G2_bls.md

formats/map_fp2_to_G2_bls.md

@@ -1 +1,23 @@
+# Test format: 'BLS12_MAP_FP2_TO_G2'
+
+maps extension field element into the G2 point
+
+## Test case format
+
+The test data is declared in a 'json' file:
+
+```
+[
+    {
+        "Input": 64 bytes as an input that is interpreted as an element of the base field.,
+        "Name": the name of the test,
+        "Expected": single G1 point 128 bytes,
+        "Gas": the cost of the gas,
+        "NoBenchmark": True/False
+    },
+    ....
+]
+```
+
+All byte(s) fields are encoded as strings, hexadecimal encoding