feat!: keep alive mechanism to detect connectivity to Discord

[amishshah]

Please describe the changes this PR makes and why it should be merged:

Adds a keep alive mechanism to the UDP socket, that allows 60 seconds for Discord to echo keep alive messages back to the sender. If 60 seconds pass, the UDP socket emits an error warning that a connection between the client and Discord is likely unavailable, causing the voice connection to attempt to reconnect.

A breaking change because connection.ping is now of type { ws: ?number, udp: ?number } instead of just ?number.

Status and versioning classification:

• Code changes have been tested against the Discord API, or there are no code changes
• This PR changes the library's interface (methods or parameters added)
• This PR includes breaking changes (methods removed or renamed, parameters moved or removed)

[codecov[bot]]

Codecov Report

Merging #89 (ebf51dc) into main (0ce79d6) will increase coverage by 1.02%. The diff coverage is 71.42%.

@@            Coverage Diff             @@
##             main      #89      +/-   ##
==========================================
+ Coverage   55.41%   56.44%   +1.02%     
==========================================
  Files          15       15              
  Lines         637      675      +38     
  Branches      143      149       +6     
==========================================
+ Hits          353      381      +28     
- Misses        282      292      +10     
  Partials        2        2              

Impacted Files	Coverage Δ
src/VoiceConnection.ts	78.57% <0.00%> (-0.71%)	:arrow_down:
src/networking/Networking.ts	3.67% <0.00%> (-0.27%)	:arrow_down:
src/networking/VoiceUDPSocket.ts	98.07% <96.77%> (+2.24%)	:arrow_up:

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