chore(deps): bump big.js and @types/big.js

Bumps [big.js](https://github.com/MikeMcl/big.js) and [@types/big.js](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/big.js). These dependencies needed to be updated together.

Updates `big.js` from 6.1.1 to 6.2.1
- [Changelog](https://github.com/MikeMcl/big.js/blob/master/CHANGELOG.md)
- [Commits](MikeMcl/big.js@v6.1.1...v6.2.1)

Updates `@types/big.js` from 6.1.2 to 6.2.1
- [Release notes](https://github.com/DefinitelyTyped/DefinitelyTyped/releases)
- [Commits](https://github.com/DefinitelyTyped/DefinitelyTyped/commits/HEAD/types/big.js)

---
updated-dependencies:
- dependency-name: big.js
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: "@types/big.js"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -61,15 +61,15 @@
     "@interlay/esplora-btc-api": "1.3.0",
     "@interlay/monetary-js": "0.7.3",
     "@polkadot/api": "10.9.1",
-    "big.js": "6.1.1",
+    "big.js": "6.2.1",
     "bitcoinjs-lib": "^5.2.0",
     "bn.js": "4.12.0",
     "cross-fetch": "^4.0.0",
     "yargs": "^17.5.1"
   },
   "devDependencies": {
     "@polkadot/typegen": "10.9.1",
-    "@types/big.js": "6.1.2",
+    "@types/big.js": "6.2.1",
     "@types/jest": "^29.5.3",
     "@types/node": "^20.5.7",
     "@types/shelljs": "0.8.12",