add EN translation for how-umi-works

[kristianmandrup]

Checklist

[ x ] documentation is changed or added

Description of change

Adds EN translations for How umi works page

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View rendered docs/docs/how-umi-works.md

[netlify]

Ant Design Pro preview using the current branch umi

Built with commit 9d67b60

https://deploy-preview-4051--pro-pre-umijs.netlify.com

[codecov]

Codecov Report

Merging #4051 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #4051   +/-   ##
======================================
  Coverage    83.9%   83.9%           
======================================
  Files         128     128           
  Lines        2528    2528           
  Branches      640     631    -9     
======================================
  Hits         2121    2121           
- Misses        398     399    +1     
+ Partials        9       8    -1

Impacted Files	Coverage Δ
packages/core/src/Config/Config.ts	60.97% <0%> (ø)	⬆️

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