Fix doc reference

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/contact/Friend.kt

@@ -7,7 +7,7 @@
  * https://github.com/mamoe/mirai/blob/master/LICENSE
  */
 
-@file:Suppress("EXPERIMENTAL_API_USAGE", "unused")
+@file:Suppress("EXPERIMENTAL_API_USAGE", "unused", "UnusedImport")
 
 package net.mamoe.mirai.contact
 

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/contact/Group.kt

@@ -7,7 +7,7 @@
  * https://github.com/mamoe/mirai/blob/master/LICENSE
  */
 
-@file:Suppress("EXPERIMENTAL_API_USAGE", "unused")
+@file:Suppress("EXPERIMENTAL_API_USAGE", "unused", "UnusedImport")
 
 package net.mamoe.mirai.contact
 

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/contact/Member.kt

@@ -7,7 +7,7 @@
  * https://github.com/mamoe/mirai/blob/master/LICENSE
  */
 
-@file:Suppress("unused")
+@file:Suppress("unused", "UnusedImport")
 
 package net.mamoe.mirai.contact
 

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/Image.kt

@@ -10,7 +10,13 @@
 @file:JvmMultifileClass
 @file:JvmName("MessageUtils")
 
-@file:Suppress("EXPERIMENTAL_API_USAGE", "unused", "WRONG_MODIFIER_CONTAINING_DECLARATION", "DEPRECATION")
+@file:Suppress(
+    "EXPERIMENTAL_API_USAGE",
+    "unused",
+    "WRONG_MODIFIER_CONTAINING_DECLARATION",
+    "DEPRECATION",
+    "UnusedImport"
+)
 
 package net.mamoe.mirai.message.data
 
@@ -36,7 +42,7 @@ import kotlin.jvm.JvmSynthetic
  *
  * ### [toString] 和 [contentToString]
  * - [toString] 固定返回 `[mirai:image:<ID>]` 格式字符串, 其中 `<ID>` 代表 [imageId].
- * - [contentToString] 固定返回 `"[图片]"`
+ * - [contentToString] 固定返回 "\[图片]"
  *
  * ### 上传和发送图片
  * @see Contact.uploadImage 上传 [图片文件][ExternalImage] 并得到 [Image] 消息

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/message/data/README.md

@@ -0,0 +1,4 @@
+# mirai Message
+消息对象. 查看 [Message] 源码内注释
+
+[Message]: Message.kt#L35