Add NEB schemas

[esoteric-ephemera]

Adding support for parsing NEB calculations and eventually ApproxNEB calculations. These are still VASP calculations, but have a directory structure which is not parseable by TaskDoc (at least meaningfully). The structure is:
./{INCAR, KPOINTS, POTCAR}
./00/POSCAR
./01/{vasprun.xml, OSZICAR, OUTCAR, CHGCAR, ... }
./02/{vasprun.xml, OSZICAR, OUTCAR, CHGCAR, ... }
...
./0N/POSCAR

Approx / NEB calculations are needed for battery cathode and alloy diffusivity calculations. These schemas will be needed for atomate2 workflows. Once Approx / NEB flows are added to atomate2, we should have full parity with atomate. This will also make it easier to host data from these calculations

Supports parsing NEB calculations (only relaxes images) and NEB + endpoints (three total calculations, two relaxes + one NEB)

Possibly worth adding run / task / calc types? Since this requires a separate doc model, maybe we should avoid this?

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 97.54098% with 3 lines in your changes missing coverage. Please review.

Project coverage is 90.49%. Comparing base (4a4b214) to head (f3b24f4).

Files with missing lines	Patch %	Lines
emmet-core/emmet/core/neb.py	97.43%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1123      +/-   ##
==========================================
+ Coverage   90.42%   90.49%   +0.07%     
==========================================
  Files         147      148       +1     
  Lines       14448    14568     +120     
==========================================
+ Hits        13065    13184     +119     
- Misses       1383     1384       +1     

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