update gitignore to allow .idea directory to exist in subdirs
update gitignore to allow .idea directory to exist in subdirs

vector-im/riot-web,vector-im/vector-web,vector-im/vector-web,vector-im/vector-web,martindale/vector,vector-im/riot-web,vector-im/riot-web,vector-im/vector-web,vector-im/riot-web,vector-im/riot-web,vector-im/vector-web,martindale/vector,vector-im/riot-web