📝 Clarify i18n directory requirements in README files (siyuan-note#35)

Author: TCOTC

README.md

@@ -115,7 +115,7 @@ A typical example is as follows:
 No matter which method is used to compile and package, we finally need to generate a package.zip, which contains at
 least the following files:
 
-* i18n/*
+* i18n/* (If the plugin supports multiple languages, language files need to be packaged to this directory, otherwise this directory is not needed)
 * icon.png (recommended size: 160*160, file size should not exceed 20KB)
 * index.css
 * index.js

README_zh_CN.md

@@ -113,7 +113,7 @@
 
 无论使用何种方式编译打包，我们最终需要生成一个 package.zip，它至少包含如下文件：
 
-* i18n/*
+* i18n/* (如果插件支持多语言，则需要将语言文件打包到该目录下，否则不需要该目录)
 * icon.png (建议尺寸为 160*160、文件大小不超过 20KB)
 * index.css
 * index.js