Add the AppImage to the README and to the release checklist.

Compiling.md

@@ -43,6 +43,17 @@ working a typical cause is that the keyboard driver, a window manager or a
 similar entity suppresses them. In this case installing ibus normally resolves
 the problem.
 
+### Creating a FlatPak AppImage
+
+FlatPak allows to create a linux executable that works like an .apk or .app file
+for Android or MacOs and that contains maxima, wxMaxima and gnuplot.
+It can be build the following way:
+
+ * Setup docker in a way that you are allowed to upload files.
+ * Download appimagetool-x86_64.AppImage an put it into the appimage folder
+ * Run 
+    make appimage
+
 ### Compiling on Mac OS X
 
 On Mac OS X you should install XCode. To build wxMaxima open the

README.md

@@ -23,3 +23,4 @@ found at https://github.com/wxMaxima-developers/wxmaxima/blob/master/Compiling.m
 
 
 ![Travis CI Build Status](https://travis-ci.org/wxMaxima-developers/wxmaxima.svg?branch=master)
+

ReleaseChecklist.txt

@@ -1,6 +1,7 @@
 - Does test/testbench_simple.wxmx work?
 - Enter the new version number into CMakeLists.txt
 - Update data/io.github.wxmaxima_developers.wxMaxima.appdata.xml
+- Update the version numbers in appimage/Dockerfile
 - Create a git tag for the release
 - Go to the releases page Github and convert the tag into a release
 - Update the release info on the download page and in release.txt