I decided to roll on my own type definitions to keep typescript compiler happy.
With a smart guy this kind of type definitions could be generated programmatically in no time!
It is a bit tedious and I feel a bit stupid doing this, but I feel it is easier for my eyes to do this way:

export interface MenuEvent extends CustomEvent {
    detail: SmartMenuItem;
}
export interface SmartMenu extends HTMLElement {
    locale: string;
}
export interface SmartMenuItem extends HTMLElement {
    item: any;
    label: any;
    value: any;
}
export interface SmartTextBox extends HTMLElement {
    locale: string;
    readonly: boolean;
    required: boolean;
    theme: string;
    value: string;
}
export interface SmartPasswordTextBox extends HTMLElement {
    locale: string;
    maxLength: number;
    minLength: number;
    passwordStrength: (password, allowedSymbols) => string;
    required: boolean;
    showPasswordIcon: boolean;
    showPasswordStrength: boolean;
    theme: string;
    tooltipArrow: boolean;
    value: string;
}
export interface SmartDropDownList extends HTMLElement {
    displayMember: string;
    locale: string;
    selectedIndexes: any[];     // array type?
    selectedValues: any[];      // array type?
    selectionMode: string;
    valueMember: string;
    clearItems();
    insert(position: number, value: any);
}