feat(packets): make skill vnum in su packet nullable

fix(packets): add header for st sub packet

chore: bump versions to support new PacketSerializer

feat(packets): add support for st buff vnums with levels

Merge pull request #32 from Rutherther/combat

Add combat extension

chore: update versions

fix(packets): Add new unknown field to ski packet, make rank of SkiSubPacket optional

fix(packets): make skill effect in SuPacket nullable

fix(packets): make su skill effect nullable

fix(packets): correctly use cast id instead of vnum in UseSkill packet

fix(packets): make correct fields in drop packet

fix(packets): make st packet buff vnums a read only list instead of list

chore: update to .NET 7

chore(packets): update version

fix(packets): make cancel unknown nullable

fix(packets): make cinfo icon short

fix(packets): make eq packet size optional

chore: update versions

feat(packets): add cancel packet

feat(packets): make position in su packet short