docs: add details for "pulling code" and "install dependencies" (#5194)

Add necessary detailled information for "Pulling code" and "Install
Dependencies", especially for when npm's version >= 7.x,
'--legacy-peer-deps' is always ignored by new comers, which will raise
installation problems as a temporary solution.

CONTRIBUTING.md

@@ -46,19 +46,19 @@ the help of [git](https://git-scm.com/download/) and work on that.
 
 ### Install Dependencies
 
-You can install all the dependencies listed in `package.json` with `npm`,
-when your npm version is 7.X or higher:
+You can install all the dependencies listed in `package.json` with `npm`:
 
 ```bash
-npm i --legacy-peer-deps
+npm i
 ```
-> Note: If you DON'T ADD `--legacy-peer-deps`, maybe dependency errors will occur
-  during installation.
+> If there's something wrong related to dependencies happending during the installation,
+you can temporarily solve it by adding `--legacy-peer-deps` when your npm version >= 7.X,
+and you can submit a PR directly in the "Issues" list to notify the author.
 
 Otherwise, you can install dependencies with the following command:
 
 ```bash
-npm i
+npm i --legacy-peer-deps
 ```
 
 ### Pull Request Guide

CONTRIBUTING.zh-CN.md

@@ -48,19 +48,17 @@
 
 ### 安装依赖
 
-你可使用 Node 自带的 `npm` 包管理工具命令安装所有在“package.json”上的必备依赖，
-当你的 npm 版本高于等于 7.X 时，你可以使用以下命令：
+你可使用 Node 自带的 `npm` 包管理工具命令安装所有在“package.json”上的必备依赖：
 
 ```bash
-npm i --legacy-peer-deps
+npm i
 ```
 
-> 请注意: 如果你不添加 `--legacy-peer-deps`, 安装过程中可能会出现与依赖性相关的错误。
-
-否则可以直接使用以下命令：
+> 请注意: 如你安装过程中看到依赖性相关的错误，而导致安装失败，且你的 npm 版本 >=7.X，临时
+解决方案是加上 `--legacy-peer-deps`，然后请及时在 Issues 里边提 PR，告知开发者。
 
 ```bash
-npm i
+npm i --legacy-peer-deps
 ```
 
 ### 提交 Pull Request