Lazy Images: Do not change image display for no JS support

[ebinnion]

To support browsers without JavaScript enabled, we made a change to hide lazily loaded images by default and then add a class with JavaScript which would show the lazy loaded image. This was done in #9780.

When released, at least two users reported issues with their images no longer being centered. This is because we were setting the display to inline-block when we decided to show the image. This PR changes that behavior so that we set display to block instead.

Ideally, we would hide the lazily loaded images by appending a class to the HTML element when the post is rendered. Then, we could just remove the class with JavaScript. That being said, I am not aware of a great way to do this in WordPress. I just pushed a second commit to do just that. Essentially, I use a not selector on the html element to hide the image, and then use JavaScript to set the class on the html element which will show the lazy loaded image.

To test:

• Checkout branch
• Ensure lazy images module is on
• Load a post with images in it, with at least one image being centered
• Ensure the centered image does not fill the post content. If it does, crop it
• Reload post and ensure that image is properly centered

Before:

After:

Fixes: #9879

[jetpackbot]

	Warnings
⚠️	"Testing instructions" are missing for this PR. Please add some

Generated by 🚫 dangerJS

[brbrr]

Tested on both desktop & mobile screensizes

LGTM 🚢