v1.6.0 release

What's Changed

• Add method to subscribe to multiple storage keys at once by @arjanz in #328
• Extensions framework by @arjanz in #329
• Fix rpc message order by @turuslan in #311
• Custom ss58_format for ss58_encode() by @arjanz in #323
• calculate weight when upload_code==false by @zabuxx in #321

New Contributors

• @turuslan made their first contribution in #311
• @zabuxx made their first contribution in #321

Full Changelog: v1.5.2...v1.6.0