Add Encoder/Decoder info to stats

[aalekseevx]

According to w3c:

https://www.w3.org/TR/webrtc-stats/#dom-rtcoutboundrtpstreamstats-encoderimplementation
https://www.w3.org/TR/webrtc-stats/#dom-rtcinboundrtpstreamstats-decoderimplementation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.86%. Comparing base (3f246fd) to head (ddf441e).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2979      +/-   ##
==========================================
- Coverage   77.92%   77.86%   -0.06%     
==========================================
  Files          89       89              
  Lines       10524    10524              
==========================================
- Hits         8201     8195       -6     
- Misses       1835     1839       +4     
- Partials      488      490       +2     

Flag	Coverage Δ
go	79.44% <ø> (-0.07%)	⬇️
wasm	63.45% <ø> (ø)

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[Sean-Der]

Thank you @kevmo314 :)