Polish Dark Mode for CSRF and Method Security diagrams

Closes gh-16151

Author: harpreets789

docs/modules/ROOT/pages/servlet/authorization/method-security.adoc

@@ -114,6 +114,7 @@ open class MyCustomerService {
 
 A given invocation to `MyCustomerService#readCustomer` may look something like this when Method Security <<activate-method-security,is activated>>:
 
+[.invert-dark]
 image::{figures}/methodsecurity.png[]
 
 1. Spring AOP invokes its proxy method for `readCustomer`. Among the proxy's other advisors, it invokes an {security-api-url}org/springframework/security/authorization/method/AuthorizationManagerBeforeMethodInterceptor.html[`AuthorizationManagerBeforeMethodInterceptor`] that matches <<annotation-method-pointcuts,the `@PreAuthorize` pointcut>>

docs/modules/ROOT/pages/servlet/exploits/csrf.adoc

@@ -82,6 +82,7 @@ To learn more about CSRF protection for your application, consider the following
 CSRF protection is provided by several components that are composed within the {security-api-url}org/springframework/security/web/csrf/CsrfFilter.html[`CsrfFilter`]:
 
 .`CsrfFilter` Components
+[.invert-dark]
 image::{figures}/csrf.png[]
 
 CSRF protection is divided into two parts:
@@ -90,6 +91,7 @@ CSRF protection is divided into two parts:
 2. Determine if the request requires CSRF protection, load and validate the token, and <<csrf-access-denied-handler,handle `AccessDeniedException`>>.
 
 .`CsrfFilter` Processing
+[.invert-dark]
 image::{figures}/csrf-processing.png[]
 
 * image:{icondir}/number_1.png[] First, the {security-api-url}org/springframework/security/web/csrf/DeferredCsrfToken.html[`DeferredCsrfToken`] is loaded, which holds a reference to the <<csrf-token-repository,`CsrfTokenRepository`>> so that the persisted `CsrfToken` can be loaded later (in image:{icondir}/number_4.png[]).