Add interface support (Typescript)

[Pilaton]

Currently, typing is only supported using "type" and not "interface".

Example for reproducing an error:

interface IData {
  title: string;
};

const { frontmatter } = await evaluate<IData>({...});

Error:

Type 'IData' does not satisfy the constraint 'Record<string, unknown>'. 

[talatkuyuk]

The type parameters TFrontmatter and TScope (in your case IData) should extend Record<string, unknown>.

The reason you got error is that the types declared with interface are a possible target for declaration merging, so their properties are not fully known. This is not the case for type aliases.

That is why you should use type instead of interface:

type IData = {
  title: string;
};

You can find additional information from here and here.

Hope it solves your issue. By the way, @Pilaton, I liked your portfolio and gave a star for the project sleep-sleep which is well structured.