支持纯色背景 (#4184)

HMCL/src/main/resources/assets/lang/I18N.properties

@@ -812,6 +812,7 @@ launcher.background.classic=Classic
 launcher.background.default=Default
 launcher.background.default.tooltip=Or "background.png/.jpg/.gif/.webp" and the images in the "bg" directory
 launcher.background.network=From URL
+launcher.background.paint=Solid Color
 launcher.background.translucent=Translucent
 launcher.cache_directory=Cache Directory
 launcher.cache_directory.clean=Clear Cache

HMCL/src/main/resources/assets/lang/I18N_zh.properties

@@ -628,6 +628,7 @@ launcher.background.classic=經典
 launcher.background.default=預設
 launcher.background.default.tooltip=自動尋找啟動器同目錄下的「background.png/.jpg/.gif/.webp」及「bg」目錄內的圖片
 launcher.background.network=網路
+launcher.background.paint=純色
 launcher.background.translucent=半透明
 launcher.cache_directory=檔案下載快取目錄
 launcher.cache_directory.clean=清理

HMCL/src/main/resources/assets/lang/I18N_zh_CN.properties

@@ -638,6 +638,7 @@ launcher.background.classic=经典
 launcher.background.default=默认
 launcher.background.default.tooltip=自动检索启动器同文件夹下的“background.png/.jpg/.gif/.webp”及“bg”文件夹内的图片
 launcher.background.network=网络
+launcher.background.paint=纯色
 launcher.background.translucent=半透明
 launcher.cache_directory=文件下载缓存文件夹
 launcher.cache_directory.clean=清理缓存