chore: release v0.2.0

[AlejandroFabianCampos]

Summary

• Bump package.json to 0.2.0
• Regenerate src/internal/version.ts via sync-version
• First public release including custom ERC-20 + native chain coin support (PR feat: support custom ERC-20 and native chain coin via customToken #5) and the chain/token expansion (PR feat: expand chains (+6 testnets) and tokens (+EURC, WETH, USDT) #4)

Test plan

• npm run verify (lint + typecheck + 82 tests pass, 9 skipped)
• After merge: npm publish --access public from main, then tag v0.2.0

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Note

Low Risk
Mostly documentation and version bumps; no runtime logic changes beyond the internal version constant.

Overview
Bumps the package release to v0.2.0 by updating package.json, package-lock.json, and regenerating src/internal/version.ts.

Refreshes README.md for the public beta release: adds a beta warning, table of contents, compatibility/versioning/changelog/contributing/security sections, updates spec links to a pinned commit, and clarifies/document usage for custom ERC-20 and native-coin settlement.

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