feat: add path payment slippage calculator - #539

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-node@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

'_error' is defined but never used

'trustlineEffect' is defined but never used

'changeTrustOperation' is defined but never used

'_error' is defined but never used

'server' is assigned a value but never used

'_signal' is defined but never used

'fundedAtMs' is defined but never used

'formatAmount' is defined but never used

'_signal' is defined but never used

'_error' is defined but never used