feat: add dedicated fireworks optional dependency (Fix #1033). (#1035)

* feat: add dedicated fireworks optional dependency

Move FireWorks dependency from docs and tests to its own optional dependency
group. This allows users to explicitly install FireWorks components with
`pip install atomate2[fireworks]` and makes the dependency structure more
modular and clear.

* Update pyproject.toml

* fix little typo.

pyproject.toml

@@ -68,6 +68,7 @@ openmm = [
     "openmm-mdanalysis-reporter>=0.1.0",
     "openmm>=8.1.0",
 ]
+fireworks = ["FireWorks==2.0.3"]
 docs = [
     "FireWorks==2.0.3",
     "autodoc_pydantic==2.2.0",