docs: add MailHog guide (#38614)
docs: add MailHog guide (#38614)

* fix(docs): make sidebar links relative

* feat(docs): add mailhog docs to sidebar
jonathanihm/freeCodeCamp,raisedadead/FreeCodeCamp,jonathanihm/freeCodeCamp,raisedadead/FreeCodeCamp,FreeCodeCamp/FreeCodeCamp,FreeCodeCamp/FreeCodeCamp