feat(server): add WEBPACK_DEV_SERVER env variable

[alexander-akait]

• This is a bugfix
• This is a feature
• This is a code refactor
• This is a test update
• This is a docs update
• This is a metadata update

For Bugs and Features; did you add new tests?

yes

Motivation / Use-Case

fixes #1533
fixes #1532

Breaking Changes

No

Additional Info

No

[codecov]

Codecov Report

Merging #1929 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1929      +/-   ##
==========================================
+ Coverage   87.96%   87.99%   +0.02%     
==========================================
  Files          15       15              
  Lines         814      816       +2     
  Branches      259      260       +1     
==========================================
+ Hits          716      718       +2     
  Misses         84       84              
  Partials       14       14

Impacted Files	Coverage Δ
lib/Server.js	85.96% <100%> (+0.06%)	⬆️

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[anshumanv]

Super neat

[hiroppy]

lgtm