Add note about single/double equals sign when used with java.security.auth.login.config

In the section

Where to Specify Which Login Configuration File Should Be Used

There's a note

https://docs.oracle.com/en/java/javase/11/security/appendix-b-jaas-login-configuration-file.html#GUID-1D5D78E1-4771-43B7-AEED-1D427A7044F0

Note:

If you use a single equals sign (=) with the java.security.auth.login.config system property, then the configurations specified by both this system property and the java.security file are used.

Add this note to every place that uses java.security.auth.login.config.