Document weak hash compatibility warning

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Co-authored-by: bytemain <13938334+bytemain@users.noreply.github.com>

Author: Copilot

docs/plugins/library/hash.md

@@ -2,6 +2,8 @@
 
 The `hash` library calculates file digests and verifies downloaded files in Lua plugins.
 
+Prefer SHA-256 or SHA-512 for new integrations. MD5 and SHA-1 are supported only for compatibility with upstream sources that do not publish stronger checksums.
+
 **Usage**
 
 ```lua

docs/zh-hans/plugins/library/hash.md

@@ -2,6 +2,8 @@
 
 `hash` 库用于在 Lua 插件中计算文件摘要并校验下载文件。
 
+新插件应优先使用 SHA-256 或 SHA-512。MD5 和 SHA-1 仅用于兼容未提供更强校验值的上游来源。
+
 **使用**
 
 ```lua