Docs: Update pip.md for introducing install packages with a specific version (#43)

Author: luckrnx09

docs/pip.md

@@ -15,6 +15,13 @@ pip install package_name1 package_name2
 ```
 It is similar to `npm install package1 package2` in JavaScript projects.
 
+If you want to install a specific version of a third-party package, you can specify it using `==`, for example:
+
+```shell
+pip install requests==2.20.0
+```
+It is similar to `npm install axios@0.21.1` in JavaScript projects.
+
 :::tip Software Repository
 The official software repository for Python is https://pypi.org.
 :::

i18n/zh-cn/docusaurus-plugin-content-docs/current/pip.md

@@ -15,6 +15,12 @@ pip install package_name1 package_name2
 ```
 它与 JavaScript 项目中的 `npm install package1 package2` 相似。
 
+如果想要安装特定版本的第三方包，可以使用 `==` 来指定，如：
+```shell
+pip install requests==2.20.0
+```
+它与 JavaScript 项目中的 `npm install axios@0.21.1` 相似。
+
 :::tip 软件仓库
 Python 的官方软件仓库为 https://pypi.org
 :::