doc: updated install script description (#3999)

close ##3975

docs/en/getting-started/installation.md

@@ -15,9 +15,15 @@ The JuiceFS client has only one binary file, you can download the pre-compiled v
 The one-click installation script is available for Linux and macOS systems and will automatically download and install the latest version of the JuiceFS client based on your hardware architecture.
 
 ```shell
+# default installation path is /usr/local/bin
 curl -sSL https://d.juicefs.com/install | sh -
 ```
 
+```shell
+# install to /tmp directory
+curl -sSL https://d.juicefs.com/install | sh -s /tmp
+```
+
 ## Install the pre-compiled client {#install-the-pre-compiled-client}
 
 You can download the latest version of the client at [GitHub](https://github.com/juicedata/juicefs/releases). Pre-compiled versions for different CPU architectures and operating systems are available in the download list of each client version. Please find the version suit your application the best, e.g.,

docs/zh_cn/getting-started/installation.md

@@ -15,9 +15,15 @@ JuiceFS 客户端只有一个二进制文件，你可以下载预编译的版本
 一键安装脚本适用于 Linux 和 macOS 系统，会根据你的硬件架构自动下载安装最新版 JuiceFS 客户端。
 
 ```shell
+# 默认安装到 /usr/local/bin
 curl -sSL https://d.juicefs.com/install | sh -
 ```
 
+```shell
+# 安装到 /tmp 目录下
+curl -sSL https://d.juicefs.com/install | sh -s /tmp
+```
+
 ## 安装预编译客户端 {#install-the-pre-compiled-client}
 
 你可以在 [GitHub](https://github.com/juicedata/juicefs/releases) 找到最新版客户端下载地址，每个版本的下载列表中都提供了面向不同 CPU 架构和操作系统的预编译版本，请注意识别选择，例如：