VnodeElementTag must be either a string or a class.

Unfortunately, TypeScript only supports strings and classes for JSX tags.
Therefore, our type definition should only allow for those two types.
see microsoft/TypeScript#14789 (comment)

js/src/@types/global.d.ts

@@ -21,9 +21,21 @@ declare type KeysOfType<Type extends object, Match> = {
  */
 declare type KeyOfType<Type extends object, Match> = KeysOfType<Type, Match>[keyof Type];
 
-declare type VnodeElementTag<Attrs = Record<string, unknown>, State = Record<string, unknown>> =
-  | string
-  | import('mithril').ComponentTypes<Attrs, State>;
+type Component<A> = import('mithril').Component<A>;
+
+declare type ComponentClass< 
+Attrs = Record<string, unknown>, C extends Component<Attrs> = Component<Attrs>> = { new (...args: any[]): Component<Attrs>, prototype: C };
+
+/**
+ * Unfortunately, TypeScript only supports strings and classes for JSX tags.
+ * Therefore, our type definition should only allow for those two types.
+ * 
+ * @see https://github.com/microsoft/TypeScript/issues/14789#issuecomment-412247771
+ */
+declare type VnodeElementTag<
+  Attrs = Record<string, unknown>,
+  C extends Component<Attrs> = Component<Attrs>
+> = string | ComponentClass<Attrs, C>;
 
 /**
  * @deprecated Please import `app` from a namespace instead of using it as a global variable.