Merge branch 'mention-dependencies' into 'releases/3.4'

mention version requirements for Dune, CMake and OPM in the CHANGELOG

See merge request !2702

(cherry picked from commit ac95cf09)

eaeabc14 mention version requirements for Dune, CMake and OPM in the CHANGELOG

CHANGELOG.md

@@ -2,6 +2,7 @@ Differences Between DuMu<sup>x</sup> 3.4 and DuMu<sup>x</sup> 3.3
 =============================================
 
 ### Improvements and Enhancements
+- __Requirements__: DuMu<sup>x</sup> still requires Dune >=2.7 and CMake >= 3.13. It was successfully tested with OPM 2021.04.
 - __Pore-network models added to DuMu<sup>x</sup>__:
     - Three fully implicit pore-network models (1p, 1pnc, 2p) have been added.
     - A quasi-static 2p PNM for the creation of pc-Sw curves has been added.