Add tip on enabling GC log without restarting the JVM (#65)

* add gc log tip

* Moving Gist to be an embedded content with ref

* Removing whitespace

---------

Co-authored-by: cchesser <cchesser@gmail.com>

Author: AnEmortalKid

docs/content/docs/memory/gc.md

@@ -184,6 +184,12 @@ java -XX:+PrintGCDetails -XX:+PrintGCDateStamps -Xloggc:gc.log -XX:GCLogFileSize
  -jar java-perf-workshop-server/target/java-perf-workshop-server-1.1.0-SNAPSHOT.jar server server.yml 
 ```
 
+### Enabling while JVM is running
+
+In higher versions of the JDK (9+), you can enable GC logging without having to restart the JVM (reference: [Thomas Darimont](https://github.com/thomasdarimont)):
+
+{{< gist thomasdarimont f89fc79491241af7a064e1b3ca2757a9 >}}
+
 ### Parsing the log
 
 For parsing the logs, we are just going to show a simple approach using [R](https://www.r-project.org/) to parse the