build(deps): bump big.js from 5.2.2 to 6.1.1

Bumps [big.js](https://github.com/MikeMcl/big.js) from 5.2.2 to 6.1.1.
- [Release notes](https://github.com/MikeMcl/big.js/releases)
- [Changelog](https://github.com/MikeMcl/big.js/blob/master/CHANGELOG.md)
- [Commits](MikeMcl/big.js@v5.2.2...v6.1.1)

---
updated-dependencies:
- dependency-name: big.js
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

package.json

@@ -24,7 +24,7 @@
       "archiver": "^3.1.1",
       "babel": "^6.23.0",
       "base-58": "0.0.1",
-      "big.js": "^5.2.2",
+      "big.js": "^6.1.1",
       "bitwise-xor": "0.0.0",
       "blake3": "^2.1.4",
       "body-parser": "^1.19.0",