feat(core): add changi network

[pierregee]

What this PR does / why we need it:

Which issue(s) does this PR fixes?:

Fixes #

Additional comments?:

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.18% 🎉

Comparison is base (889c877) 66.12% compared to head (d5e141b) 66.30%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #156      +/-   ##
==========================================
+ Coverage   66.12%   66.30%   +0.18%     
==========================================
  Files          29       29              
  Lines         927      932       +5     
  Branches      155      158       +3     
==========================================
+ Hits          613      618       +5     
  Misses        314      314              

Files Changed	Coverage Δ
packages/walletkit-core/src/api/environment.ts	100.00% <100.00%> (ø)
packages/walletkit-core/src/api/network.ts	78.94% <100.00%> (+1.16%)	⬆️
packages/walletkit-core/src/api/whale.ts	100.00% <100.00%> (ø)

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