The latter part of the question is done by in dev.cljs.edn adding a row like ^{:watch-dirs ["src/cljs" "src/cljc" "env/dev/cljs" "env/dev/cljc" "external-dependencies"].
dev.cljs.edn
^{:watch-dirs ["src/cljs" "src/cljc" "env/dev/cljs" "env/dev/cljc" "external-dependencies"]