Cclib

The first preliminary release of v2.0 that corresponds to our upcoming paper.

**Summary of changes since last version**

- New parser: xTB
- Support parsing number of CPUs and memory used for Gaussian, ORCA, and Turbomole
- New attributes for the NBO parser
- Tested support for Python 3.8 through 3.11
- Many developer-facing improvement and several fixes, see [changelog](https://github.com/cclib/cclib/blob/release-1.8.1/doc/sphinx/changelog.rst) for details

**Summary of changes since last version**
* [GSoC 2023] New language bindings: Julia (https://github.com/cclib/Cclib.jl)
* [GSoC 2023] New parsers: GAMESS *.dat and NBO
* New attributes: nmrcouplingtensors for NMR spin-spin couplings, rotconsts for rotational constants
* New method: compute CM5 charges
* Added metadata support for solvent parameters and excited state methods
* Expanded attributes supported for MOLDEN writer
* Many additional improvements and fixes, see changelog for details

**Summary of change since last version**
* Support for excited states, vibrational frequency and thermochemistry for NWChem
* Better metadata support for point group detection
* Several other improvements and fixes, see changelog for details