This diff adds .cjs extension to commonjs bundle. Why do we need to save build as cjs?

If you try to require() an ES module (a package with "type": "module" in its package.json), Node.js will throw an error. This is because require() is a feature of CommonJS, not ES modules.

We build package as ES Modules and as CommonJS. We have "type": "module" in the package.json, so if user wants to require package and use it is commonjs module they have an error.

We can simply avoid it by adding .cjs extension to the module file. From nodejs documentation:

Within a "type": "module" package, Node.js can be instructed to interpret a particular file as CommonJS by naming it with a .cjs extension

Also this diff:

• Adds prototypes of deserialization methods
• Renames Transactions to Messages