Function createAd

createAd(id, options):
    | NitroAd
    | Promise<NitroAd>
    | Promise<NitroAd[]>
    | null
Creates an ad placement.
Parameters
- id: string
  The id for the placement. For most placement types, this should be the id of a div that the ad will fill.
- options: NitroAdOptions
  The options object containing settings for the placement.
Returns
    | NitroAd
    | Promise<NitroAd>
    | Promise<NitroAd[]>
    | null
Depending on loading state, this may return a promise or an object.
Remarks
The id used for a placement must be unique on the page it appears, and should be a stable identifier for the ad placement. Randomized values should not be used for id.

Example
```
// basic usage
window.nitroAds.createAd('banner-1', {
    sizes: [[728, 90]],
});
```
Example
```
// you can wrap with Promise.resolve to handle case where return may be a promise or not
Promise.resolve(window.nitroAds.createAd('banner-1', {})).then((ad) => {
    // now save ad object for later use
});
```
Example
```
// you can also just use await in an async function
let ad = await window.nitroAds.createAd('banner-1', {});
```