Fix *page-name* to *page-index* conversion

[swaldhoer]

• Fix page-name to page-index conversion as needed since drawio 27.0.2
• Add Windows CI tests

Open point: What to do with older drawio versions? Should this be detected at runtime and then go back to 0-based indexing?

Issues:

• Closes page-name maps to wrong diagrams with current drawio versions #106
• Closes Tests only run on Linux #72

[swaldhoer]

@modelmat would it be possible to receive some feedback on the approach?

[swaldhoer]

I have added 36720f9 which should create backwards compatibility with the the version that is currently used in testing (20.6.2). This is needed as older drawio-versions create slightly differently sized images.

I am a bit confused why the tests for versions <= 27.0.2 pass at all, as the index in the *.rst files are all 1-based, but the the older drawio versions expect 0-based page index input. I would expect that all test cases that rely on the directive matching :page-(index|name): only pass for 27.0.2 or later.

Anyhow, I will look into this