up: update NEWS.md for version 0.2.0 with improvements and new features

refs #12

NEWS.md

+# optirrigBEET 0.2.0 : Beet it !
+
+* Improve the pakage format (adapt optirrigCORE)
+* Take into account S3 classes for optirrigCORE import functions
+* Complete overhaul of function documentation
+* Correction of a problem with the installation tokens
+* New visual (adapted from optirrigCORE) for the site 
+* Rework of certain functions add for the beet case
+* Correction of a bad calculation of the stress
+* Docker environment added
+
 # optirrigBEET 0.1.0
 
 * An Optirrig Add-on for beetroot crop optimisation
-