fix: types for the proxy option

[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?

No need

Motivation / Use-Case

fix types

Breaking Changes

No

Additional Info

No

[codecov]

Codecov Report

Merging #4173 (609a298) into master (415fb66) will increase coverage by 0.13%.
The diff coverage is 93.75%.

@@            Coverage Diff             @@
##           master    #4173      +/-   ##
==========================================
+ Coverage   92.27%   92.40%   +0.13%     
==========================================
  Files          14       14              
  Lines        1540     1541       +1     
  Branches      589      590       +1     
==========================================
+ Hits         1421     1424       +3     
+ Misses        110      108       -2     
  Partials        9        9              

Impacted Files	Coverage Δ
lib/Server.js	93.72% <93.75%> (+<0.01%)	⬆️
lib/servers/WebsocketServer.js	94.87% <0.00%> (+5.12%)	⬆️

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