Document that StructuredLoggingJsonMembersCustomizer implementations may optionally take constructor parameters

[quaff]

Similar to

spring-boot/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/env/EnvironmentPostProcessor.java

Lines 37 to 46 in f9aedf5

	* Since Spring Boot 2.4, {@code EnvironmentPostProcessor} implementations may optionally
	* take the following constructor parameters:
	* <ul>
	* <li>{@link DeferredLogFactory} - A factory that can be used to create loggers with
	* output deferred until the application has been fully prepared (allowing the environment
	* itself to configure logging levels).</li>
	* <li>{@link ConfigurableBootstrapContext} - A bootstrap context that can be used to
	* store objects that may be expensive to create, or need to be shared
	* ({@link BootstrapContext} or {@link BootstrapRegistry} may also be used).</li>
	* </ul>

[wilkinsona]

Thanks, @quaff. I polished things a bit to match the javadoc of org.springframework.boot.logging.structured.StructuredLogFormatter in the same package.