Added a PcapSnooper class

[willnix]

I built a bumble HCI logging bridge for live logging with Wireshark.
It simply plugs together bumble's snooper concept with a Wireshark extcap script via a named pipe.
You can see the result here:
https://github.com/willnix/bumble-wireshark

I thought the bumble part of it could be useful to others, hence I'm opening this PR.
The class implements a bumble snooper that writes PCAP records. It can write to either a file or a named pipe.
The latter is what I use to bridge with Wireshark but I thought logging to a PCAP file might sometimes also be handy.

I ran invoke project.lint -d "", fixed what came up and generally tried to stick very close to the existing structure.
What I'm not super happy with is the text duplication in the docstring, but I wasn't really sure what else to do.

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[willnix]

I fixed the formatting issues that came up in the checks by running black and making minimal manual adjustments.

[zxzxwu]

You can use invoke project.pre-commit to verify your commit locally.

[zxzxwu]

Should have annotation here

[willnix]

You can use invoke project.pre-commit to verify your commit locally.

Ah perfect! I'll do that and update soon.

[willnix]

Somehow my local project.pre-commit does not run mypy, so I ran it manually and fixed what came up.