Add AppExtension subspec back to Mixpanel.podspec
Add AppExtension subspec back to Mixpanel.podspec

mixpanel/mixpanel-iphone,depop/mixpanel-iphone,depop/mixpanel-iphone,mixpanel/mixpanel-iphone,mixpanel/mixpanel-iphone,carezone/mixpanel-iphone,carezone/mixpanel-iphone,mixpanel/mixpanel-iphone,depop/mixpanel-iphone,depop/mixpanel-iphone,mixpanel/mixpanel-iphone