v1.5.0 release candidate

Dear people!

Uff... After Moodle made some changes in its last version 4.2 and we had changes JSXGraph in 1.5.0, our filter had to be fundamentally adjusted.
But it's finally done! Today we can announce a new version.
The biggest change on the usage side is that in the future no JSXGraph versions can be loaded from CDN (which is also really unsafe). Instead, we now deliver all 33 versions. So these are stored on your server and work without external web access! You can simply select the version in the administrator menu or switch on the automatic function - this way the latest version is always used with every new filter update.

Because so much has changed under the hood, the status of this version is still "release candidate" as a precaution. Please report if you discover any errors. We have already tested over 70 different version combinations (https://github.com/jsxgraph/moodle-filter_jsxgraph/blob/main/tests/matrices.md). Perhaps you can add to this matrix.
If there are no more problems, the new version (which will probably be released with JSXGraph 1.6.0) will be a stable version again.

Have fun using it!
Alfred and Andreas