docs: show optional [area] arg for /gsd:map-codebase in README#866

amanape wants to merge 1 commit intogsd-build:maingsd-build/get-shit-done:mainfrom

amanape:docs/map-codebase-arg-hintamanape/get-shit-done:docs/map-codebase-arg-hintCopy head branch name to clipboard