Include the supported OpenModelica version in documentation / unittest #348

Up to now, two points are listed as requirements in the README file:

• Python 3.x supported
• PyZMQ is required

An in unittest, the the following properties are varied

• Python version (3.10, 3.12)
• OS (Windows 11, Ubuntu) [latest for each]

However, shouldn't there be a statement (testing?) regarding the supported version of OpenModelica?

Based on issue #196, I think OpenModelica > 1.18 is a must have!

Would be nice to be able to include this in 4.0.0; some basic testing for the (oldest / newest) OpenModelica version could be done using the docker capability included in this version, i.e. add tests for some important capabilities in test.tests_docker; currently OpenModelica 1.25 is used.