tar 0.2.0-nullsafety

Memory-efficient, streaming implementation of the tar file format

0.2.0-nullsafety

Most of the tar package has been rewritten, it's now based on the implementation written by Garett Tok Ern Liang in the GSoC 2020.

• Added tar prefix to exported symbols.
• Remove MemoryEntry. Use TarEntry.data to create a tar entry from bytes.
• Make WritingSink private. Use tarWritingSink to create a general StreamSink<tar.Entry>.
• TarReader is now a StreamIterator, the transformer had some design flaws

0.1.0-nullsafety.1

• Support writing user and group names
• Better support for PAX-headers and large files

0.1.0-nullsafety.0

• Initial version