[doc][release notes] add three more tickets solved in the 1.56 release
Merge pull request #122 from mkaravel/doc/release_notes-1.56

Release notes for 1.56 (solved tickets)
[doc] Add ticket to release notes
[algorithms][is_valid] use bg::partition to check whether the interior
rings of a polygon (that are disjoint from each other and from the
exterior ring) do not overlap with each other