Add references to Copernik.eu Log4j components (#3534)

This change adds references to the Log4j plugins from my personal "Extensions for Log4j and Tomcat" to the documentation.

Co-authored-by: Volkan Yazıcı <volkan@yazi.ci>
diff --git a/src/site/antora/modules/ROOT/pages/manual/lookups.adoc b/src/site/antora/modules/ROOT/pages/manual/lookups.adoc
index 5a1411e..889ff6c 100644
--- a/src/site/antora/modules/ROOT/pages/manual/lookups.adoc
+++ b/src/site/antora/modules/ROOT/pages/manual/lookups.adoc
@@ -945,7 +945,12 @@
 [#third-party]
 == Third-party lookups
 
-The following additional lookups are available from third-party vendors:
+[IMPORTANT]
+====
+These lookups are provided by **third-party** vendors and are not maintained by the
+link:{logging-services-url}[Apache Logging Services]
+(Log4j, Log4cxx, Log4net) project.
+====
 
 [#KubernetesLookup]
 === Kubernetes Lookup
@@ -972,6 +977,24 @@
 https://docs.spring.io/spring-boot/reference/features/logging.html#features.logging.log4j2-extensions.environment-properties-lookup[Spring Boot documentation]
 for more details.
 
+[#TomcatLookup]
+=== Tomcat Lookup
+
+[cols="1h,4"]
+|===
+| Syntax
+|
+`tomcat:<key>`
+
+where `key` is one of the
+https://oss.copernik.eu/tomcat/3.x/components/log4j-tomcat#TomcatLookup-keys[supported Tomcat Lookup keys]
+| Dependency | https://oss.copernik.eu/tomcat/3.x/components/log4j-tomcat#installation[`eu.copernik:log4j-tomcat`]
+|===
+
+The Tomcat Lookup allows retrieving the names of the currently active Tomcat engine, host and application context.
+See
+https://oss.copernik.eu/tomcat/3.x/components/log4j-tomcat#TomcatLookup[Copernik.eu Tomcat Lookup documentation] for more details.
+
 [#extending]
 == Extending
 
diff --git a/src/site/antora/modules/ROOT/partials/manual/systemproperties/properties-logger-context.adoc b/src/site/antora/modules/ROOT/partials/manual/systemproperties/properties-logger-context.adoc
index e3e10e8..dc6b071 100644
--- a/src/site/antora/modules/ROOT/partials/manual/systemproperties/properties-logger-context.adoc
+++ b/src/site/antora/modules/ROOT/partials/manual/systemproperties/properties-logger-context.adoc
@@ -64,6 +64,21 @@
 {logging-services-url}/log4j/jakarta/log4j-jakarta-web.html#jndi[Web application]
 for details.
 
+There are also third-party context selector implementations:
+
+[IMPORTANT]
+====
+These context selectors are provided by **third-party** vendors and are not maintained by the
+link:{logging-services-url}[Apache Logging Services]
+(Log4j, Log4cxx, Log4net) project.
+====
+
+https://oss.copernik.eu/tomcat/3.x/components/log4j-tomcat#TomcatContextSelector[`eu.copernik.log4j.tomcat.TomcatContextSelector`]::
+Selects the currently active Tomcat web application and creates synchronous loggers.
+
+https://oss.copernik.eu/tomcat/3.x/components/log4j-tomcat#TomcatContextSelector[`eu.copernik.log4j.tomcat.TomcatAsyncContextSelector`]::
+Selects the currently active Tomcat web application and creates xref:manual/async.adoc[asynchronous loggers].
+
 [id=log4j.loggerContext.shutdownHookEnabled]
 == `log4j.loggerContext.shutdownHookEnabled`