docs: improve documentation for dts.alias (#1391)

Author: Timeless0911

packages/plugin-dts/README.md

@@ -147,7 +147,7 @@ pluginDts({
 
 Configure the path alias for declaration files.
 
-`alias` will be merged with `compilerOptions.paths` configured in `tsconfig.json` and `alias` has a higher priority.
+The path aliases configured in `alias` should be resolved relative to the directory specified by `compilerOptions.baseUrl` in `tsconfig.json`. These aliases will be merged with `compilerOptions.paths`, and `alias` takes higher precedence.
 
 In most cases, you don't need to use `alias`, but consider using it when you need to use path alias only in declaration files without wanting to affect JavaScript outputs. For example, map the declaration file of `foo` to `./compiled/foo`.
 
@@ -159,6 +159,13 @@ pluginDts({
 });
 ```
 
+At this time, when [redirect.path](#redirectpath) is enabled, the import path of `foo` in the declaration file will be redirected to `./compiled/foo`.
+
+```diff
+- export * from 'foo';
++ export * from './compiled/foo';
+```
+
 ### autoExternal
 
 - **Type:** `boolean`

website/docs/en/config/lib/dts.mdx

@@ -235,7 +235,7 @@ When `dts.autoExtension` is set to `true`, the declaration file extension will b
 
 Configure the path alias for declaration files.
 
-`dts.alias` will be merged with `compilerOptions.paths` configured in `tsconfig.json` and `dts.alias` has a higher priority.
+The path aliases configured in `dts.alias` should be resolved relative to the directory specified by `compilerOptions.baseUrl` in `tsconfig.json`. These aliases will be merged with `compilerOptions.paths`, and `dts.alias` takes higher precedence.
 
 In most cases, you don't need to use `dts.alias`, but consider using it when you need to use path alias only in declaration files without wanting to affect JavaScript outputs. For example, map the declaration file of `foo` to `./compiled/foo`.
 
@@ -254,6 +254,13 @@ export default {
 };
 ```
 
+At this time, when [redirect.dts.path](/config/lib/redirect#redirectdtspath) is enabled, the import path of `foo` in the declaration file will be redirected to `./compiled/foo`.
+
+```diff title="index.d.ts"
+- export * from 'foo';
++ export * from './compiled/foo';
+```
+
 ### dts.tsgo
 
 - **Type:** `boolean`

website/docs/zh/config/lib/dts.mdx

@@ -235,7 +235,7 @@ export default {
 
 用于配置类型声明文件的路径别名。
 
-`dts.alias` 会与 `tsconfig.json` 中配置的 `compilerOptions.paths` 合并，且 `dts.alias` 具有更高的优先级。
+在 `dts.alias` 中配置的路径别名，其相对路径应基于 `tsconfig.json` 中 `compilerOptions.baseUrl` 所指定的目录。这些别名会与 `compilerOptions.paths` 进行合并，且 `dts.alias` 的优先级更高。
 
 大部分情况下，你不需要使用 `dts.alias`，但当你需要在类型声明文件中使用路径别名却不希望影响 JavaScript 产物时，可以考虑使用它。比如，将 `foo` 的类型声明文件指向 `./compiled/foo`。
 
@@ -254,6 +254,13 @@ export default {
 };
 ```
 
+此时，当 [redirect.dts.path](/config/lib/redirect#redirectdtspath) 开启时，类型声明文件中对 `foo` 的导入路径将会被重定向为 `./compiled/foo`。
+
+```diff title="index.d.ts"
+- export * from 'foo';
++ export * from './compiled/foo';
+```
+
 ### dts.tsgo
 
 - **类型：** `boolean`