Add ability to add decoding options to tshark invocation

[Hodkinson]

It's useful to set tshark option flags, in order to tune how the pcap file or capture is decoded. For example fragmentation options, or how disassemblers are used.

This adds an option function to the builder, so that these options can be provided.

Eg

let builder = rtshark::RTSharkBuilder::builder()
  .input_path("/tmp/my.pcap")
  .option("ip.defragment:false")
  .option("inap.ssn:146");