V0.2.0 release changelog, pyproject.toml update, codecov fix (#148)

* update changelog for v0.2.0

* minor modification for PR template

* formatting fixes

* formatting and typos

* remove contributors bc they aren't linked

* update pyproject.toml to v0.2.0

* lint

* try regressing codecov

Finalize readme, docs, and coverage (#100 - #104)

* plot speedup

* change import line

* conf.py docs fix

* restyle TorchSim -> torch-sim

* small typo fix

* tweak err messages

* small trajectory fix and ignore unbatched in codecov

* remove seemingly unneeded Structure/Atoms/PhonopyAtoms stubs in torch_sim/io.py

* set coverage target

* fix toml

* multi line string

* tweak doc strings

* switch away from .png

* move speedup up in readme

* fix broken links and set threshold differently

* docs fix

* delete codevoc threshhold attempt

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Co-authored-by: Janosh Riebesell <janosh.riebesell@gmail.com>