Use semantic versioning for PyPI package (#20)

Use [semantic versioning](https://semver.org/) (MAJOR.MINOR.PATCH) for
the PyPI package, instead of YY.MM, as suggested in
#18 (comment).

Based on the scheme and the FAQ at
https://semver.org/#how-should-i-deal-with-revisions-in-the-0yz-initial-development-phase,
it seems to me like we should start with 0.1.0.

Author: EZoni

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "pals_schema"
-version = "25.08"
+version = "0.1.0"
 dependencies = [
   "pydantic",
   "pyyaml",