feat: allow to set client.webSocketURL.protocol

[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?

WIP on tests

Motivation / Use-Case

When you proxy webpack dev server and proxy uses https you can't change protocol of web socket client URL without this feature

Breaking Changes

No

Additional Info

No

[codecov]

Codecov Report

Merging #3380 (689a173) into master (7e86922) will decrease coverage by 0.06%.
The diff coverage is 85.71%.

@@            Coverage Diff             @@
##           master    #3380      +/-   ##
==========================================
- Coverage   95.76%   95.70%   -0.07%     
==========================================
  Files          33       33              
  Lines        1299     1304       +5     
  Branches      381      384       +3     
==========================================
+ Hits         1244     1248       +4     
- Misses         51       52       +1     
  Partials        4        4              

Impacted Files	Coverage Δ
client-src/utils/createSocketURL.js	96.42% <50.00%> (-3.58%)	⬇️
lib/utils/DevServerPlugin.js	97.22% <100.00%> (+0.05%)	⬆️
lib/utils/normalizeOptions.js	98.38% <100.00%> (+0.01%)	⬆️

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