fix install documents

Author: Rintan

docs/installation_guide.md

@@ -288,6 +288,43 @@ git submodule update --recursive --remote
 
    </details>
 
+5. Edit [`/src/mastodon-material.scss`](../src/mastodon-material.scss) like below.
+   
+   Diff
+
+   ```diff
+   - @use '../../../application'; // for git submodule install
+   - //@use '../application'; // for copying file install
+   + //@use '../../../application'; // for git submodule install
+   + @use '../application'; // for copying file install
+   
+   @use 'mastodon-material';
+   ```
+   
+   <details>
+   <summary>Before</summary>
+
+   ```scss
+   @use '../../../application'; // for git submodule install
+   //@use '../application'; // for copying file install
+   
+   @use 'mastodon-material';
+   ```
+   
+   </details>
+
+   <details>
+   <summary>After</summary>
+
+   ```scss
+   //@use '../../../application'; // for git submodule install
+   @use '../application'; // for copying file install
+   
+   @use 'mastodon-material';
+   ```
+   
+   </details>
+
 5. Follow the steps from 4. in [Installing multiple Mastodon Material (by using submodules)](installation_guide.md#installing-multiple-mastodon-material-by-using-submodules).
 
 ### Updating Mastodon Material (by copying files)

docs/installation_guide_ja.md

@@ -288,7 +288,44 @@ git submodule update --recursive --remote
 
    </details>
 
-5. [複数のMastodon Materialを導入する(サブモジュール)](installation_guide_ja.md#複数のMastodon-Materialを導入する(サブモジュール))の4.以降に従ってください。
+5. [`/src/mastodon-material.scss`](../src/mastodon-material.scss)を以下のように編集してください。
+   
+   Diff
+
+   ```diff
+   - @use '../../../application'; // for git submodule install
+   - //@use '../application'; // for copying file install
+   + //@use '../../../application'; // for git submodule install
+   + @use '../application'; // for copying file install
+   
+   @use 'mastodon-material';
+   ```
+   
+   <details>
+   <summary>変更前</summary>
+
+   ```scss
+   @use '../../../application'; // for git submodule install
+   //@use '../application'; // for copying file install
+   
+   @use 'mastodon-material';
+   ```
+   
+   </details>
+
+   <details>
+   <summary>変更後</summary>
+
+   ```scss
+   //@use '../../../application'; // for git submodule install
+   @use '../application'; // for copying file install
+   
+   @use 'mastodon-material';
+   ```
+   
+   </details>
+
+6. [複数のMastodon Materialを導入する(サブモジュール)](installation_guide_ja.md#複数のMastodon-Materialを導入する(サブモジュール))の4.以降に従ってください。
 
 ### Mastodon Materialのアップデート(ファイルコピー)
 

src/mastodon-material.scss

@@ -1,2 +1,4 @@
-@use 'application';
+@use '../../../application'; // for git submodule install
+//@use '../application'; // for copying file install
+
 @use 'mastodon-material';