Merge pull request #2317 from ethereum-optimism/willc-contributingdoc

docs: update contributing.md for exit code 137

CONTRIBUTING.md

@@ -138,6 +138,8 @@ docker-compose build
 docker-compose up
 ```
 
+**If a node process exits with exit code: 137** you may need to increase the default memory limit of docker containers
+
 Finally, **if you're running into weird problems and nothing seems to be working**, run:
 
 ```bash