Fix relative links to .drawio files that are not colocated with a pages markdown file

[noltedennis]

This pull request fixes #12 .

This pull request provides a permanent fix such that files can be properly specified with relative paths - even to different hierarchy levels. Prior, a workaround was deployed that just stripped ../ from the start of relative paths. This, however, had negative side effects when the .drawio files were not colocated with the markdown page (e.g. if they are stored in a separate media file structure):

• paths then had to specified with an extra hierarchy layer, breaking IDE completions
• even then, mkdocs very own build pipeline threw a warning in the build process, detailing that it cannot find the referenced file (because it does not strip ../ in the beginning of paths)

In addition, a third markdown page is introduced in the example that can be used to test the plugin for this edge case.

[tuunit]

As this repository doesn't seem to be maintained anymore :( I've created a fork and integrated your Commits in it as well

https://github.com/tuunit/mkdocs-drawio https://pypi.org/project/mkdocs-drawio/