feat(game): add inventory api

feat(packets): add n_run for npc operations

feat(packets): add packet for moving through portals

feat(packets): add packets for managing inventory

feat(game): add api for mates (company, stay, send back)

feat: add pet positions to walk command

Resolves #33

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

chore(test): update tests

feat(packets): pass nullable to packet serializers

Merge pull request #46 from Rutherther/feat/act4

Add Act4 status processing

feat(game): emit Act4StatusReceived event upon receiving act4 info

Resolves #43

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