Document how to configure ServletContext init parameters

Closes gh-47951

Author: wilkinsona

spring-boot-project/spring-boot-docs/src/docs/antora/modules/reference/pages/web/servlet.adoc

@@ -556,6 +556,14 @@ The single `onStartup` method provides access to the javadoc:jakarta.servlet.Ser
 
 
 
+[[web.servlet.embedded-container.context-initializer.init-parameters]]
+==== Init Parameters
+
+Init parameters can be configured on the javadoc:jakarta.servlet.ServletContext[] using `server.servlet.context-parameters.*` properties.
+For example, the property `server.servlet.context-parameters.com.example.parameter=example` will configure a `ServletContext` init parameter named `com.example.parameter` with the value `example`.
+
+
+
 [[web.servlet.embedded-container.context-initializer.scanning]]
 ==== Scanning for Servlets, Filters, and listeners