Extension broken since Sphinx 7.2.0

[Grokzen]

We noticed that Sphinx have deprecated old os.path lib and moved over to new Path lib since version 7.2.2 in the following commit
sphinx-doc/sphinx@49d8304 in the following MR sphinx-doc/sphinx#11526 that caused a breaking change that cause the latest release of this lib to break down

Due to this change that the variable app.outdir is now a PosixPath instead of a str. This cause the following line of code

sphinx-material/sphinx_material/__init__.py

Line 74 in ac74442

filename = app.outdir + "/sitemap.xml"

to break down as it can't join PosixPath + str. The exception we get is TypeError: unsupported operand type(s) for +: 'PosixPath' and 'str' but the stacktrace is not existing in sphinx errors.

We will fork this and submit a PR and use our fork for now until this can be released with a fix