implementation of low rank ot via factor relaxation paper

Author: fegounna

RELEASES.md

@@ -8,6 +8,7 @@
 - Automatic PR labeling and release file update check (PR #704)
 - Reorganize sub-module `ot/lp/__init__.py` into separate files (PR #714)
 - Fix documentation in the module `ot.gaussian` (PR #718)
+- Implement low rank through Factor Relaxation with Latent Coupling
 
 #### Closed issues
 - Fixed `ot.mapping` solvers which depended on deprecated `cvxpy` `ECOS` solver (PR #692, Issue #668)