file permission support in erl_tar:add/3,4

[sg2342]

Is your feature request related to a problem? Please describe.

I want to create a tar archive that contains an executable file. From memory without disk I/O.

Describe the solution you'd like

erl_tar:add/3,4 supports to set atime, mtime, ctime, gid and uid of the file/directory in the archive. It should also allow to set mode.