slack-client-1.16.8

What's Changed

• Add missing call subtype by @szabowexler in #378
• add zip filetype by @seoterran in #381
• bump basepom to 63, upgrade jackson to 2.18, add required pom metadata fields by @jaredstehler in #382

Full Changelog: slack-client-1.16.7...slack-client-1.16.8