feat(game-servers): game server notifications on Discord

[garrappachc]

Send admin notification whenever a game server gets added or removed.

[codecov]

Codecov Report

Merging #944 (edab44b) into master (6cda591) will decrease coverage by 0.00%.
The diff coverage is 94.87%.

@@            Coverage Diff             @@
##           master     #944      +/-   ##
==========================================
- Coverage   94.23%   94.23%   -0.01%     
==========================================
  Files         152      154       +2     
  Lines        3038     3069      +31     
  Branches      282      288       +6     
==========================================
+ Hits         2863     2892      +29     
- Misses        174      176       +2     
  Partials        1        1              

Impacted Files	Coverage Δ
...ns/discord/services/admin-notifications.service.ts	92.50% <86.66%> (-1.44%)	⬇️
src/events/events.ts	100.00% <100.00%> (ø)
...ame-servers/controllers/game-servers.controller.ts	100.00% <100.00%> (ø)
src/game-servers/services/game-servers.service.ts	98.57% <100.00%> (+0.06%)	⬆️
src/plugins/discord/notifications/colors.ts	100.00% <100.00%> (ø)
...plugins/discord/notifications/game-server-added.ts	100.00% <100.00%> (ø)
...ugins/discord/notifications/game-server-removed.ts	100.00% <100.00%> (ø)
src/plugins/discord/notifications/index.ts	100.00% <100.00%> (ø)

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