chore: add example for basic wrappers

[xiaohuoni]

添加约定式的 wrappers 例子，为了回复 #6562

Checklist

• npm test passes
• tests are included
• documentation is changed or added
• commit message follows commit guidelines

Description of change

• any feature?
• close https://github.com/umijs/umi/ISSUE_URL

---

View rendered examples/basic-wrappers/README.md

[codecov]

Codecov Report

Merging #6570 (7a39753) into master (680bed7) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #6570   +/-   ##
=======================================
  Coverage   84.77%   84.77%           
=======================================
  Files         157      157           
  Lines        3599     3599           
  Branches      991      991           
=======================================
  Hits         3051     3051           
  Misses        538      538           
  Partials       10       10           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 680bed7...7a39753. Read the comment docs.