Refactor config

[lazzzis]

1. 把 title 变量全部放到 .env 中
2. 引入 .env.sample , 用的时候改名为 .env，避免 git pull 的时候的冲突
3. 同理，data/1000 -> data/example
4. 改变 manage.js 的用法。node manage.js setup 初始化，node manage.js update-fe 下载最新的前端文件。git pull 更新后端文件

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.72%. Comparing base (b83513e) to head (813b10f).
Report is 5 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #81      +/-   ##
==========================================
+ Coverage   85.71%   85.72%   +0.01%     
==========================================
  Files          45       45              
  Lines        1155     1156       +1     
==========================================
+ Hits          990      991       +1     
  Misses        165      165              

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