Add release notes page for version 0.6.0

Patrole 0.6.0 has been released [1].
This commit adds a new page for 0.6.0 release notes.

[1] https://review.opendev.org/#/c/672485/

Change-Id: Ife0ac2e4a38d96ea312e6c410f85b4e0a97c2f4a
2 files changed