What problem does this feature solve?

Currently IDE extensions cannot extract the types of locally registered components, which makes it difficult to support strong typings of components inside SFC templates, see vuejs/language-tools#80.

What does the proposed API look like?

Expose the component types as generics (if possible):

export declare interface ComponentOptionsBase<LocalComponents extends Record<string, Component>, Props, ...> {
    components?: LocalComponents;
    ...
}