issues with complex types for modifiers

[aklkv]

while trying to switch to v2 in jelhan/ember-style-modifier#323

I noticed that with following signature:

type CSSStyles =
  | Partial<CSS.Properties>
  | Partial<CSS.PropertiesHyphen>
  | { readonly [key: `--${string}`]: string };


export interface StyleModifierSignature {
  Element: Element & ElementCSSInlineStyle;
  Args: {
    Positional: CSSStyles[];
    Named: CSSStyles;
  };
}

errors no longer shown when incorrect value like number is passed in. maybe related to #886 or sounds more similar to #613