chore: add example graphs & update docs

plugins/cpu/cpu_by_group

@@ -7,9 +7,9 @@ set -e
 
 =head1 NAME
 
-cpu_by_group - Monitors cpu usage for all processes on a system and groups them into graphs by either cgroup, system processes or kernel threads
+cpu_by_group - Monitors cpu time for all processes on a system and groups them into graphs by either cgroup, system processes or kernel threads
 
-=head1 CONFIGURATION
+=head1 DESCRIPTION
 
 Works similar as good ol' cpu_by_process, but groups processes by either their cgroup, system proceses or kernel threads to produce smaller graphs.
 
@@ -18,12 +18,25 @@ For user cgroups the user id will be resolved to the corresponding user name.
 
 The plugin keeps track of previously running processes in MUNIN_STATEFILE
 
+=head2 EXAMPLE GRAPHS
+
+There are 3 example graphs which were all automatically generated by this plugin.
+
+- System-day -> system processes (processes without a cgroup)
+- KThread-day -> kernel threads
+- caddy-day -> A docker compose project named caddy, with a single container named caddy and a single caddy process 
+
+=head1 CONFIGURATION
+
 For full docker support, ensure that munin can access docker. F.e. run munin with the docker group:
 
 [cpu_by_group]
 	group docker
 
-Requires bash v4.3+
+=head1 REQUIREMENTS
+
+- bash v4.3+
+- docker access rights (if using docker)
 
 =head1 AUTHOR