fix: make content-type of readme explicit

Author: dlugoschvincent

pyproject.toml

@@ -2,7 +2,7 @@
 name = "zalfmas-common"
 version = "0.1.24"
 description = "Common code for ZALF MAS projects"
-readme = "README.md"
+readme = { file = "README.md", content-type = "text/markdown" }
 authors = [{ name = "Michael Berg-Mohnicke", email = "michael.berg@zalf.de" }]
 requires-python = ">=3.10,<3.13"
 dependencies = [