Update CHANGELOG.md

* Add entry on SubsamplingVTKWriter
* Add section 'Deprecated' with entry for `subsamplingLevel`

[ci skip]

CHANGELOG.md

@@ -4,6 +4,8 @@
 ## Unreleased
 
 ### Added
+* DORiE now employs a `SubsamplingVTKWriter` for higher output precision.
+    Subsampling levels are controlled via the new key `output.subsamplingLevel`.
 * Automatic deployment of `devel` and stable DORiE Docker Images to Docker Hub
 * Automatic update of the DUNE environment Docker Image for `master` builds
 * CI pipeline now also compiles a Debug build with the LLVM Clang compiler
@@ -21,7 +23,12 @@
     sequential ones. This significantly improves performance for large problems.
 * Change compilation order which reduces RAM usage when compiling in parallel.
 * Decentralization of the header system so that in most of the header files are 
-	independent of each other  
+	independent of each other
+
+### Deprecated
+* `output.subsamplingLevel` is optional and defaults to 0 if not given
+    explicitly in the config file. The key will become mandatory in future
+    versions.
 
 ### Fixed
 * The source code is now compatible to the Clang LLVM compiler.