release: v2.1.1

Version bumped in server.py, pyproject.toml, the PWA header and the
docs/api.md example; SW cache v124 -> v125.

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "pysim-otaman-server"
-version = "2.1.0"
+version = "2.1.1"
 description = "HTTP REST server wrapping pysim for the OTAMan PWA"
 requires-python = ">=3.8"
 # pysim is a git-only dependency installed explicitly by setup.bat/setup.sh.