switch browser manifest.json to manifest.edn by default
switch browser manifest.json to manifest.edn by default

output format is controlled by the name.
:manifest-name "manifest.json" will print it as JSON instead.

closes #139

thheller/shadow-cljs,thheller/shadow-devtools,thheller/shadow-cljs,thheller/shadow-devtools,thheller/shadow-devtools,thheller/shadow-cljs,thheller/shadow-cljs,thheller/shadow-devtools