Update README and ReleaseNotes for 5.0.6

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

README.md

@@ -11,10 +11,10 @@
 ![Build Status](https://github.com/subsurface/subsurface/workflows/Ubuntu%2020.10%20/%20Qt%205.14--/badge.svg)
 ![Build Status](https://github.com/subsurface/subsurface/workflows/openSUSE/Tumbleweed%20/%20Qt%20latest--/badge.svg)
 
-This is the README file for Subsurface 5.0.5
+This is the README file for Subsurface 5.0.6
 
 Please check the `ReleaseNotes.txt` for details about new features and
-changes since Subsurface 5.0.4 (and earlier versions).
+changes since Subsurface 5.0.5 (and earlier versions).
 
 Subsurface can be found at http://subsurface-divelog.org
 
@@ -49,10 +49,10 @@ development version) you can either get this via git or the release tar
 ball. After cloning run the following command:
 
 ```
-git checkout v5.0.5  (or whatever the last release is)
+git checkout v5.0.6  (or whatever the last release is)
 ```
 
-or download a tarball from http://subsurface-divelog.org/downloads/Subsurface-5.0.5.tgz
+or download a tarball from http://subsurface-divelog.org/downloads/Subsurface-5.0.6.tgz
 
 Detailed build instructions can be found in the INSTALL file.
 

ReleaseNotes/ReleaseNotes.txt

@@ -2,6 +2,16 @@
 
 = _Subsurface_ Release Notes
 
+New in _Subsurface_ 5.0.6
+~~~~~~~~~~~~~~~~~~~~~~~~~
+- statistics: implement ordering of categorical bar charts
+- divelist: Don't attempt to compute SAC for CCR dives
+- profile: fix editing of time / duration (profile of edited dive was not shown)
+- profile: rewrite of part of the implementation which resulted in performance improvements
+- small dive computer fixes:
+   - Uwatec/Scubapro dive computers: restore the original standard gravity factor
+   - Garmin: fix gas change event parsing
+
 New in _Subsurface_ 5.0.5
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 - store dive computer 'fingerprints' with the dive log data, including in the cloud