Extension fails to find templates in Sphinx templates_path

[goerz]

It appears that the doctr_versions_menu extension will not use a custom doctr-versions-menu.js_t in the templates_path defined in Sphinx' conf.py.

The problem is in the following code:
https://github.com/goerz/doctr_versions_menu/blob/63ec6aa0037b1c62cf46ba632a56a59f17700aac/src/doctr_versions_menu/ext.py#L26-L28

Here, we use app.config.templates_path, which by default is ['_templates'], where _templates is supposed to be relative to the folder in which conf.py resides. However, we use it here as a path relative to the current working directory. Generally, there will be no folder _templates in the current working directory, so the extension falls back to str(Path(__file__).parent / '_template', i.e. the built-in default template. The custom template will not be used, and there will be no warning.

Strangely, the tests didn't catch this, even though we explicitly tests that custom templates work. This must be some weird detail of sphinx-testing. 🤷