Support APEX 20.1 and JDK 8u251

[fuzziebrain]

[robertsondas]

Hi Fuzziebrain
I followed your steps in https://github.com/fuzziebrain/docker-apex-stack

but below error i am getting

Unknown or unsupported database version and/or edition.
#####Building Docker Image for Oracle Database 18.4.0
Checking Docker version.
does not have Express Edition available.