Merge branch 'master' into fittable-params

.gitattributes

@@ -1 +1,2 @@
 pint/extern/_version.py export-subst
+src/pint/extern/_version.py export-subst

CHANGELOG-unreleased.md

@@ -12,6 +12,7 @@ the released changes.
 - `WAVE` parameters can be added to a `Wave` model with `add_wave_component()` in `wave.py` 
 - Moved design matrix normalization code from `pint.fitter` to the new `pint.utils.normalize_designmatrix()` function.
 - Made `Residuals` independent of `GLSFitter` (GLS chi2 is now computed using the new function `Residuals._calc_gls_chi2()`).
+- Upgraded versioneer for compatibility with Python 3.12
 - Creation of `Fitter` objects will fail if there are free unfittable parameters in the timing model.
 - Only fittable parameters will be listed as check boxes in the `plk` interface.
 ### Added

src/pint/extern/__init__.py

@@ -1,2 +1,6 @@
 # __init__.py for pint/extern
 """External/third-party modules that are distributed with PINT."""
+
+from . import _version
+
+__version__ = _version.get_versions()["version"]