Add the KOFR index

[jongbongan]

Korea Overnight Financing Repo Rate (KOFR) published by Korea Securities Depository (KSD)

Please refer to
(1) https://www.bok.or.kr/eng/main/contents.do?menuNo=400399 (Overview)
(2) https://www.kofr.kr/main.jsp (Detailed information)

[CLAassistant]

All committers have signed the CLA.

[coveralls]

coverage: 72.671% (-0.003%) from 72.674%
when pulling 61793d8 on jongbongan:south_korea_ois
into 4cf0296 on lballabio:master.

[lballabio]

Thanks! May you check the CLAassistant comment? It might be because you committed with a different author email which is not associated to your GitHub account.

[jongbongan]

Thanks! May you check the CLAassistant comment? It might be because you committed with a different author email which is not associated to your GitHub account.

I will. Thank you.

[jongbongan]

I think I would rather make another PR whose differences are same with this. (3357428 is actually my corporate PC, which is not a GitHub user.)

[sweemer]

You can just amend the author on the commit and force push the branch.

[jongbongan]

You can just amend the author on the commit and force push the branch.

I will try it.

[jongbongan]

I rebased it to remove the author 3357428. Thanks @sweemer @lballabio