[Feature] Implementations for Discord integration

[tintinkung]

From #31 Since that issue kinda get buried and inactive.

The Plot-System have flaws in itself with the review system where integrating with discord will highly improve it.

I'll point it out here:

1. Directions for what to do after finishing the tutorial is not very welcoming

   • Thanks for doing the tutorial, now go create a plot
   • These message answer only few thing
   • What if the builder is stuck? what to do after finishing a plot?

2. Minecraft UI is trash for complex reviewing system and how high-standard BTE is

3. Builder have no way of communicating or asking about their created plot

   • Right now we resort to the builder doing the work of having to provide:
     • their plot location
     • their plot reference
     • their progress images
   • Then its depend of each team's support system for whether the builder can get their help answered

4. Language?

   • Currently builder have opt-in to figuring out minecraft UI, find the language UI, then find their language.
   • If only there's a system to link their language role where most builder already came from discord server

ASEAN BTE Team Solution

So I wrote a bare-minimum integration code using java JDA v4 (discord api) for one-way event handling.

Connector Plugin via DiscordSRV-PlotSystem

Refer to its Wiki for the detailed system overview.

Known issues is noted inside the plugin's github repo.

• Discord account linking
  • Handled via DiscordSRV plugin because I can't be bother to make it myself
• Plot Tracking
  • Every created plot will be tracked via discord forum channel (as a thread)
  • Builders can then get their plot information, share their thread to ask questions, get their review feedbacks.
• Extensions for the review system
  • Reviewers can then be notified for each submitted/on-going plot
  • Review can formatted nicely with discord markdown
  • The owner get mentioned, without having to join the minecraft server, open messy minecraft UI, peak at big minecraft pixelated text.
• Language Integrations
  • Not yet implemented

Implementations

I've created a pull request #176 for the legacy Plot-System V4.X.X
Read the pull request for more details.

Of course the pr can be rejected, my release is available in ASEAN BTE fork of Plot-System
https://github.com/ASEAN-Build-The-Earth/Plot-System/tree/legacy/4.2.X