Add distro's introduction to README.md (#13470)

Co-authored-by: Jay DeLuca <[email protected]>
Co-authored-by: Trask Stalnaker <[email protected]>

Author: 3 people

README.md

@@ -104,6 +104,11 @@ having to create a separate distribution or to fork this repository. For example
 custom samplers or span exporters, set new defaults, and embed it all in the agent to obtain a
 single jar file.
 
+## Creating an agent distribution
+
+[Distribution](examples/distro/README.md) provides guidance on creating a separate distribution, serving as a collection of examples for extending the functionality of the OpenTelemetry Java instrumentation agent. It also demonstrates how to repackage the agent while incorporating custom features.
+[Agent extensions](#creating-agent-extensions) are recommended instead for most users as they are simpler and do not require rebuilding with each OpenTelemetry Java agent release.
+
 ## Manually instrumenting
 
 For most users, the out-of-the-box instrumentation is completely sufficient and nothing more has to