add Chinese MOD instructions.

src/main/resources/assets/cavedust/lang/en_us.json

@@ -1,4 +1,5 @@
 {
+  "modmenu.descriptionTranslation.cavedust": "Makes dust underground that scales with depth!",
   "menu.cavedust.title": "Cave Dust",
   "menu.cavedust.global.false": "Cave Dust: Disabled",
   "menu.cavedust.global.true": "Cave Dust: Enabled",

src/main/resources/assets/cavedust/lang/zh_cn.json

@@ -1,4 +1,5 @@
 {
+  "modmenu.descriptionTranslation.cavedust": "在地下生成随深度增加而变化的尘埃！",
   "menu.cavedust.title": "洞穴尘埃",
   "menu.cavedust.global.false": "洞穴尘埃: 功能启用",
   "menu.cavedust.global.true": "洞穴尘埃: 功能禁用",