dpkt readme needs to explain what the package does

[brifordwylie]

@obormot @kbandla so I noticed that the Readme has no explaining for what dpkt is/does. So shrug... I start a strawman and you guys can add/improve.

Adding some feedback from obormot..

"The dpkt package is a lightweight Python for network packet parsing and unpacking. Dpkt processes packets individually as a stream and is therefore fast and memory efficient. Since dpkt focuses on individual packets it does NOT provide reassembly functionality (like full HTTP requests/responses)."

Shrug.. please feel free to improve this ^

[obormot]

...and what it does NOT too! E.g. we get many repeated issues/questions on ip/tcp/etc. stream reassembly or things that require underlying reassembly (like full HTTP requests/responses).
Also I suggest establishing guidelines for submitting issues - e.g. if it's a pcap failure, always attach the pcap and the piece of code that fails with explanation.