Set type of package to module

[leebyron]

It's great that this package builds and publishes esmodule ready code via the "exports" key in package.json, however if you try to import this package from another esmodule file, node will present an error SyntaxError: Cannot use import statement outside a module.

It's likely this has gone unnoticed since most will be importing this directly from TypeScript, which compiles code down to another target, but this will reproduce if you import in a vanilla node environment.

There are two ways to fix this, either the esmodule code needs to use the .mjs extensions, or the package.json needs to include "type": "module". Either will tell node that the referenced file should be interpreted as a module instead of a script.

I've proposed what was easier to introduce, adding the line to package.json

[quantizor]

@leebyron have you tested this change in a normal cjs project?

[quantizor]

Superceded by #500