release 0.6.0

Features:

• issue #91: support Policies for both queues and exchanges.

Fixes:

• issue #92: fix queue crash when node restarted.

Improvements:

• issue #82: rebalance exchange caches when cluster size increases.
  Credits: megwill4268

Minimum supported versions:

• RabbitMQ 3.11.0
• Erlang 25.0
• Elixir 13.0