docs: Update installation instructions

- Update composer installation command to include --prefer-source flag
- Add section for installation issues
- Provide commands to fix installation issues
- Update Backend -> Helpers -> Extensions section

README-zh_CN.md

@@ -22,7 +22,7 @@
 ### Composer 安装
 
 ```bash
-composer require guanguans/dcat-login-captcha -v
+composer require guanguans/dcat-login-captcha --prefer-source -v
 ```
 
 ### 安装问题([https://github.com/guanguans/dcat-login-captcha/issues/39](https://github.com/guanguans/dcat-login-captcha/issues/39))

README.md

@@ -25,6 +25,15 @@
 composer require guanguans/dcat-login-captcha --prefer-source -v
 ```
 
+### Installation issues([https://github.com/guanguans/dcat-login-captcha/issues/39](https://github.com/guanguans/dcat-login-captcha/issues/39))
+
+```shell
+composer config -g repo.packagist composer https://packagist.org -v
+composer clear-cache -v
+composer remove guanguans/dcat-login-captcha -v
+composer require guanguans/dcat-login-captcha --prefer-source -v
+```
+
 ### Backend -> Helpers -> Extensions
 
 Enable this extension.