Add the PL/SQL keyword ELSIF

[aandteogkaffi]

sqlparse/sqlparse/keywords.py

Line 727 in 11a6b7d

KEYWORDS_ORACLE = {

https://docs.oracle.com/cd/E11882_01/appdev.112/e25519/reservewords.htm#r6c1-t4

[aandteogkaffi]

I wasn't sure if this specifically meant PL/SQL, but if so adding it would help out with some of my work.

If this is the right place and a good idea, I can do the work. Just wanted to make sure.