feat(packets): add packets for managing inventory

Merge pull request #47 from Rutherther/feat/pass-nullable

Pass CanBeNull to string serializer and converter

feat(packets): make NullableWrapper a struct for less allocations

fix(packets): add forgotten nullable check to inline enum generator

fix(packets): correctly handle nullables in NullableStringConverter

feat(packets): update packets to not use nullable if not needed

feat(packets): pass nullable to packet serializers

feat(packets): add use partner skill packet

Merge pull request #45 from Rutherther/feat/mates

Add support for mates

fix(packets): correctly represent finfo

fix(packets): make nullable wrapper a class

feat(packets): add nullable wrapper to represent a compoud type that may be null as a whole

fix(packets): correctly deserialize list with generic elements inline

chore(game): add missing documentation

fix(packets): correctly deserialize list with nullable elements inline

feat(game): add mates processing

feat(game): add revive handling

fix(packets): finfo contains just one update

feat(packets): add party stat packet

feat(packets): add pet and partner skill packets