Expose p50k_edit encoding (openai#32)

Author: fritzo

tests/test_simple_public.py

@@ -24,3 +24,5 @@ def test_encoding_for_model():
     assert enc.name == "gpt2"
     enc = tiktoken.encoding_for_model("text-davinci-003")
     assert enc.name == "p50k_base"
+    enc = tiktoken.encoding_for_model("text-davinci-edit-001")
+    assert enc.name == "p50k_edit"

tiktoken_ext/openai_public.py

@@ -84,4 +84,5 @@ def cl100k_base():
     "r50k_base": r50k_base,
     "p50k_base": p50k_base,
     "cl100k_base": cl100k_base,
+    "p50k_edit": p50k_edit,
 }