fix github language stats getting dominated by jupyter notebook (#1076)

Co-authored-by: Akash Mahajan <akash.mahajan@microsoft.com>
Co-authored-by: Jong Wook Kim <jongwook@openai.com>

.gitattributes

@@ -0,0 +1,3 @@
+# Override jupyter in Github language stats for more accurate estimate of repo code languages
+# reference: https://github.com/github/linguist/blob/master/docs/overrides.md#generated-code
+*.ipynb linguist-generated