Add bitcoinjs-lib test comment

[lastmjs]

azle/examples/bitcoinjs-lib/test/pretest.ts does an unexpected npm install on a sibling project. Please add a descriptive comment for newcomers to the codebase, as this is not an obvious thing.

[bdemann]

We were able to fix this in https://github.com/demergent-labs/azle/pull/1782 by adding the sibling project as a dependency in the package.json and by preserving symlinks in the azle build process, the tsconfig and ts-node