Pygaps

* ⚠️🐍 Minimum python is now 3.8, maximum increased to 3.13.
* Fixed various accumulating issues and bugs and deprecations.
* Fully transitioned to 'pyproject.toml' build specifier.

* Added a new function that calculates the enthalpy of adsorption using a method
proposed by Whittaker et al in `pygaps.characterisation.enth_sorp_whittaker`.
Thanks to L Scott Blankenship for contribution!
* Updated AIF parser to latest version. Thanks to Jack Evans for contribution.
* Refactored DR/DA calculations.
* Docs updating to fix issue 42
* Added data types to excel output parsing to fix edge cases where these were not
correctly parsed.
* Testing correctly on Python 3.11.
* Fixed various accumulating issues and bugs and deprecations.

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* Drop python 3.6
* Parsing of instrument files is now spun off into
a separate package for ease of maintenance.
See: https://github.com/AIF-development-team/adsorption-file-parser
* Completely switched to `setuptools_scm` for versioning (no public-facing
changes)

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* AIF can read/write all isotherm types (models/points).
Also further improved parsing of units and metadata.
* Quantachrome `txt` files are now fully parseable
* Isotherm data can now be other things beside numbers.
* Added two standard isotherms (silica+carbon black). Can be used in thickness calculations.

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* Better error handling of nonphysical mesoporous PSD models
* CLI now prints package version with `--version` argument

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Fixes:

* AIF file export now more reliable with custom properties
* Isotherm models correctly instantiate their variables (parameters would
otherwise be shared between instances)