Add missing extension to emulator build to allow package installation
<arg value="--isForCompanion" />
<arg value="--isForEmulator" />
<arg value="--includeDangerousPermissions" />
+ <arg value="--extensions" />
+ <arg value="edu.mit.appinventor.companionextras.CompanionExtras" />
<arg value="--outputDir" />
<arg value="${public.build.dir}" />
<arg value="--outputFileName" />
