message: [skip ci] modify release note
diff: We are pleased to announce the release 3.3.0 of the GUDHI library.
  -As a major new feature, the GUDHI library now offers a persistence-based clustering algorithm and weighted Rips complex using DTM.
  +As a major new feature, the GUDHI library now offers a persistence-based clustering algorithm, weighted Rips complex using DTM
  +and edge collapse.
  -We are now using GitHub to develop the GUDHI library, do not hesitate to [fork the GUDHI project on GitHub](https://github.com/GUDHI/gudhi-devel). From a user point of view, we recommend to download GUDHI user version (gudhi.3.3.0.tar.gz).
  +The GUDHI library is hosted on GitHub, do not hesitate to [fork the GUDHI project on GitHub](https://github.com/GUDHI/gudhi-devel).
  +From a user point of view, we recommend to download GUDHI user version (gudhi.3.3.0.tar.gz).
  Below is a list of changes made since GUDHI 3.2.0:
  @@ -21,6 +23,10 @@ Below is a list of changes made since GUDHI 3.2.0:
  - [Clustering](https://gudhi.inria.fr/python/latest/clustering.html)
  - Python implementation of [ToMATo](https://doi.org/10.1145/2535927), a persistence-based clustering algorithm
  +- [Edge Collapse](https://gudhi.inria.fr/doc/latest/group__edge__collapse.html) of a filtered flag complex
  + - This C++ implementation reduces a filtration of Vietoris-Rips complex from its graph to another smaller
  + flag filtration with the same persistence.
  +
  - [Bottleneck distance](https://gudhi.inria.fr/python/latest/bottleneck_distance_user.html)
  - Python interface to [hera](https://github.com/grey-narn/hera)'s bottleneck distance
  