fix(GuildMember): account for joinedTimestamp as well
fix(GuildMember): account for joinedTimestamp as well

Lewdcario/discord.js,hydrabolt/discord.js,SpaceEEC/discord.js,hydrabolt/discord.js,appellation/discord.js,appellation/discord.js,Lewdcario/discord.js,appellation/discord.js,Lewdcario/discord.js,SpaceEEC/discord.js,SpaceEEC/discord.js,hydrabolt/discord.js