minimal readme

README.md

@@ -1,2 +1,23 @@
 # vmtk-build
-Build VMTK
+
+Build VMTK via GitHub Actions
+
+Build VTK, ITK and VMTK automatically on push. On release, add tar.gz
+archives to the release.
+
+## Ubuntu 20.04 (Focal)
+
+To use you need to install a suitable python. APT packages are
+`libpython3.8` or `libpython3.9`.
+
+You also need to install OpenGL etc packages (libopengl0, libglx0,
+libxt6).
+
+So:
+
+```
+apt-get install libpython3.8 libopengl0 libglx0 libxt6
+```
+
+
+