Elphmod

* Support for `mpi4py` version 4.0.0
* Loading of *.xyz* files (needed for i-PI example) was broken in version 0.27

* Faster calculation of long-range terms
* Syntax upgrade (absolute imports, Python 3)
* New function to define uniform meshes
* Fixed methods to shift orbitals and atoms
* Various new unit tests

* Small but relevant bugfix in new EPW interface

* Superconductivity calculations on large supercells
* Improved documentation (patches, conventions, source-code links)
* New format for Wigner-Seitz data (*wigner.fmt*)
* Fan-Migdal self-energy and Green-Kubo conductivity
* Size-consistent Ewald parameter (as in development version of QE)
* Allen-Dynes formula with strong-coupling and shape corrections
* Improved handling of atomic projections (phase, spin-orbit coupling)

* Improved MD driver and i-PI example
* Calculation of band velocity without finite differences
* Documentation of indices of matrix elements
* Export of coupling in EPW format (*.epmatwp*)
* Transformation of coupling to arbitrary real-space meshes
* Cleanup of routines related to Wigner-Seitz cell
* Subpackage `elphmod.models` for nearest-neighbor model input data

* QE-7.3 support (cDFPT patch, no longer included in source distribution)
* pyproject.toml-based build with reviewed requirements
* Scripts replaced by entry points (for editable installs and portability)
* Phonons and faster forces from MD driver using sparse coupling matrices
* Official PNG version of logo
* Read the Docs theme
* First unit test
* Various bugfixes and optimizations