Summary:
related to T15996
- docs are now buildable with b2 (in a very simplified way) like mysql docs
- change Async.MQTT5 -> Boost.MQTT5, async_mqtt5 namespace to boost::mqtt5 namespace
- once changes are approved, Ill update all tabs to 4 spaces in .qbk files
Reviewers: ivica
Reviewed By: ivica
Subscribers: iljazovic, miljen
Differential Revision: https://repo.mireo.local/D33373
