1.16: added coloring with minimessage, added new language system

This is quite a big update in terms of internal changes:

• Replaced the way of coloring and formatting components, now using minimessage format, instead of &-color codes.
  • For more information please see: https://github.com/justEli/Coins/wiki/Formatting-messages-and-components
• Replaced the way of handling language, now using locale language files in the folder 'locale'.
  • There is no more support for the old language files, as it was too complex to keep supporting it.
  • Default languages added to the plugin: English (en-US), Nederlands (nl-NL), Español (es-ES), français (fr-FR), Italiano (it-IT), 简体中文 (zh-CN), Deutsch (de-DE), Svenska (sv-SE), עברית (he-IL), Русский (ru-RU), or create your own custom file.
• Moved to namespaced keys for parsing item types and entity types.
• Added separate Spigot and Paper integration, using paper-plugin.yml.
• Dropped support for versions older than Minecraft 1.21.
• Fixed an issue with LevelledMobs not recognizing Coins properly.

Default values were changed for the following config options:

locale: 'en-US'
pickup-message: '<up>↑ <money>{currency}{amount}'
dropped-coin-name: '<coins>Coin'
withdrawn-coin-names:
  singular: '<var>{amount} <coins>Coin'
  plural: '<var>{amount} <coins>Coins'
coin-item: 'minecraft:sunflower'
sound-name: 'minecraft:item.armor.equip_gold'
withdraw-message: '<coins>→ <money>{currency}{amount}'
death-message: '<down>↓ <money>{currency}{amount}'

.. including 'mob-multiplier' and 'block-drops'.

Added new wiki pages:

• https://github.com/justEli/Coins/wiki/Formatting-messages-and-components
• https://github.com/justEli/Coins/wiki/Player-head-coin-texture
• https://github.com/justEli/Coins/wiki/Custom-model-data-coin-texture

Also posted the project to Modrinth (currently under review): https://modrinth.com/plugin/coinsplugin

What's Changed

• add: locale/zh-CN.json by @chenxuuu in #70

Full Changelog: 1.15...1.16