Improve ImageEmbedBuilderWeb in example

[clia]

When using the example in Web browsers, the image is displayed abnormally or not displayed.

The browser debug console outputs:

Height of Platform View type: [https://some.com/some.jpg] may not be set. Defaulting to `height: 100%`.
Set `style.height` to any appropriate value to stop this message.

Width of Platform View type: [https://some.com/some.jpg] may not be set. Defaulting to `width: 100%`.
Set `style.width` to any appropriate value to stop this message.

So I added the width and height style for the image, setting it to 'auto', to make it show properly.

[mozartee]

Because of your setting of auto with width and height, how to set the ImageEmbedBuilderWeb's constraints property?

[clia]

Because of your setting of auto with width and height, how to set the ImageEmbedBuilderWeb's constraints property?

The behavior of these widths and heights is a bit messy and weird, sometimes they still don't show up, and I don't know how to handle them perfectly. Do you have any good ideas?