Add MPEG-TS reader and writer common package

[gokuljs]

Add MPEG-TS reader and writer support for H.264 and H.265 to pion/format as a new pion/format/mpegts package.

The package should work as a standalone Go library that applications can import directly. It should preserve video timing without decoding or re-encoding. It should also work well with Pion WebRTC applications and fit the proposed pion/rtp v3 API in pion/rtp#362.

This issue continues the design and implementation work from pion/webrtc#3169.

[gokuljs]

@JoTurk For the initial scope, should this support only H.264/H.265 video as discussed in pion/webrtc#3169, or should audio be included as well?

[JoTurk]

@gokuljs IMO, I think the initial scope should be mpeg-ts primitives, timings, pat/pmt, pes, psi etc
Then the first elementary stream support should be hevc and h264. i think, but feel free to go with any plan.

Related but i think the package structure should format/[container] and readers and writers should be in the same package, function options, NewWriter(...options) NewReader(...options). what do you think? if you agree I'll copy the ogg reader and writer to here.

[gokuljs]

@JoTurk Yes, I agree with this structure. format/[container] is what I had in mind as well. Keeping the reader and writer in the same package, with functional options for NewReader and NewWriter, makes sense.

For MPEG-TS, I’ll start with the core primitives and timing, including PSI tables such as PAT and PMT, and PES. Then I’ll add H.264 and HEVC elementary stream support. I’ll keep audio out of the initial scope.

Please go ahead with copying the Ogg reader and writer. It will also give me the package conventions to follow.

[gokuljs]

#3