Fix quotation marks in f-string

[dolph]

Closes: #59

[ConnorTroy]

It appears that there are several other f-strings with the same issue: main...ConnorTroy:mkdocs-drawio-exporter:f-string-quotes

[mriedem]

Thanks for posting this. @LukeCarrier have you thought about running flake8 or some other static code check during CI runs?

[LukeCarrier]

Hey, thanks for fixing this. I'm happy to review any CI and release improvements but have barely enough time to maintain this as is.

In this case having a wider test matrix covering older Python versions prior to 3.12 would have caught this, and that's a quick win here (#61).

[LukeCarrier]

Have taken @ConnorTroy's linked diff above and added a missing __future__ annotation for the typings introduced in 0.9.0, both in #62. #61 should ensure I don't break everyone again in the next release :-)