Export FlatMetadata type

[solonovamax]

it would be great if you could export the FlatMetadata type:

imagetools/packages/core/src/output-formats.ts

Lines 19 to 29 in 3d4f02b

	/**
	* The flat object emitted by the `as=metadata` output format: the raw sharp
	* metadata of the image combined with the final output `width`, `height` and
	* `format`, plus the image URL. The applied-transform directives are not
	* included, since they cannot be reconstructed from a cached file, keeping the
	* output identical between cache hits and misses.
	*/
	type FlatMetadata = Omit<Metadata, 'format'> & {
	format: string
	src: string
	}

I'd like to be able to use this for a typescript module declaration:

declare module "*as=metadata" {
    import {FlatMetadata} from "imagetools-core";
    const value: FlatMetadata | FlatMetadata[];
    export default value;
}

declare module "*as=meta" {
    import {FlatMetadata} from "imagetools-core";
    const value: FlatMetadata | FlatMetadata[];
    export default value;
}

however, because it's not exported currently, I need to vendor the type.

also, it would be great if the flatten function could also be exported, as I have my own custom output format which previously used Metadata from sharp (similar to how this package used to), but I'd like to replace it with FlatMetadata.