[ImageCacheIt] Pass headers when using `getItem` static method

[williamjuan027]

When using ImageCacheIt in template, you could pass in a http header via the headers property (as specified in the docs), like this:

<ImageCacheIt 
        [headers]="headers"
        [src]="imageUrl"></ImageCacheIt>

Would it be possible to also pass in the headers property when using the getItem method to load images that require a header?

Perhaps something like this?

ImageCacheIt.getItem(imageUrl, { headers: headers });

[triniwiz]

Yes this should be possible with a little change