fix: add missing typescript export for init args

[nathanosdev]

Overview
The JavaScript bindings generated by Candid include an init function that can prepare the IDL object necessary to encode init args. There is no corresponding export on the TypeScript bindings so TypeScript will complain when trying to import this function.

Requirements
The TypeScript bindings should match the JavaScript bindings and export the init function.

Considered Solutions
This can be worked around on the developer side by adding a custom declaration file.

Recommended Solution
I recommend to add this to Candid's declaration generation so it's not necessary to workaround on the developer side.

Considerations
This will have no impact on security or performance.
It is not a breaking change because it's only adding a new exported type.
Maintenance cost should be minimal on this.