Add release notes page for version 0.8.0

Patrole 0.8.0 has been released [1].
This commit adds a new page for 0.8.0 release notes.

[1] https://review.opendev.org/#/c/703523/

Change-Id: I61333ba564d6f067dd8063fd89847ac58ed93d1d
2 files changed