fix(skymp5-server): fix SP3 list functions API & upload an example

[Pospelove]

[!IMPORTANT] Fixes off-by-one errors in SP3ListStaticFunctions and SP3ListMethods in ScampServer.cpp and adds wip_sp3.js as an SP3 implementation example.

• Bug Fixes:
  • Fix off-by-one error in SP3ListStaticFunctions() and SP3ListMethods() in ScampServer.cpp by using an index variable i instead of result.Length() to set array elements.
• New Example:
  • Add wip_sp3.js as an incomplete test/example for SP3 implementation with TODOs for typed return values, class name normalization, and method naming conventions.

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