fix(uui-input): validators should convert to string

Author: iOvergaard

packages/uui-input/lib/uui-input.element.ts

@@ -327,12 +327,12 @@ export class UUIInputElement extends FormControlMixin(
     this.addValidator(
       'tooShort',
       () => this.minlengthMessage,
-      () => !!this.minlength && (this._value as string).length < this.minlength
+      () => !!this.minlength && String(this._value).length < this.minlength
     );
     this.addValidator(
       'tooLong',
       () => this.maxlengthMessage,
-      () => !!this.maxlength && (this._value as string).length > this.maxlength
+      () => !!this.maxlength && String(this._value).length > this.maxlength
     );
   }