fix(DiscordJS): fix the way that the client filler gets the shard ID in v12

[EndBug]

I noticed that the v12 ShardClientUtil does not contain the ID of the shard you're using. I figured out that the only way to get the shard id is to get a guild and take it from there.

I'm not sure about this though: that strategy relies on the fact that every guild cached will have the same shard ID. Are we sure about that? Is it possible that selecting a random guild will result in the wrong shard ID? Is there a better alternative (like maybe taking the most used shard ID)?

Let me know what you think

[codecov]

Codecov Report

Merging #184 (e66761e) into master (2be800d) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #184   +/-   ##
=======================================
  Coverage   97.67%   97.68%           
=======================================
  Files          45       45           
  Lines        1205     1210    +5     
  Branches      192      194    +2     
=======================================
+ Hits         1177     1182    +5     
  Misses         27       27           
  Partials        1        1           

Impacted Files	Coverage Δ
src/Interface/Clients/DiscordJS.ts	100.00% <100.00%> (ø)

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[Snazzah]

You can read off of client.options.shards (shard ID) and client.options.shardCount.

Actually, since client.options.shards can apparently hold multiple IDs, should probably add a check if the shards option is an array. And just mark the shard as unsupported if there is more than one ID.

[EndBug]

I've updated the getter, is it better now?

[Snazzah]

After this, LGTM