[FEAT] Use instanceOf check for parent element (in settings)

[tobium]

Currently we only can specify the parentElement by a text css selector. It would be good to set the parentElement as HTMLElement instance too.

To allow this, we have to changed the following code in cupertino-pane.ts

from
if (this.settings.parentElement) {
this.settings.parentElement = document.querySelector(
this.settings.parentElement
);
} else {
this.settings.parentElement = this.el.parentElement;
}

to
if (this.settings.parentElement && !this.settings.parentElement instanceOf HTMLElement) {
this.settings.parentElement = document.querySelector(
this.settings.parentElement
);
} else {
this.settings.parentElement = this.el.parentElement;
}

[roman-rr]

Hello @tobium
Thank you for proposal.
Could you please create pull request with this simple changes ?

[roman-rr]

@tobium let me know if you need this as soon as possible. Otherwise better new pull request, so you will be in contributors also.