fix parsing mention (#171)
fix parsing mention (#171)

resolve #106.
misskey-delta/Misskey-Web,armchair-philosophy/Misskey-Web,misskey-delta/Misskey-Web,Tosuke/Misskey-Web,armchair-philosophy/Misskey-Web,armchair-philosophy/Misskey-Web,Tosuke/Misskey-Web,Tosuke/Misskey-Web,misskey-delta/Misskey-Web,Tosuke/Misskey-Web