Merge branch 'main' into main

Bump program version to 6.4.0 (grimme-lab#428)

Guard time estimate printout in hessian with omp critical (grimme-lab…

…#350)

Bump version number to 6.3.2 (grimme-lab#291)

Bump xtb version number to 6.3.1 (grimme-lab#254)

Add possibility to set numerical accuracy in API (grimme-lab#232)

- also give access to max iterations and electronic temperature
- add possibilities to access wavefunction
- remove initial newline from returned buffer

Patch user input to mopac to ensure gradient printout (grimme-lab#147)

- also warn user that input has been patched

bump version to 6.3.0

bump version to 6.2.2 (grimme-lab#71)

Bugfix: ANC-opt hessian read-in error