Disable the creation of srcset on SVGs

[dkotter]

Description of the Change

In #23 we changed some behavior on how the height and width of SVGs are set. Previously those values were set to false, which in some instances just gets translated to zero. But this caused some issues in a few places, like the block editor, as technically those values are supposed to be integers and if those aren't converted to integers, it will cause PHP errors. We fixed this by using the actual height and width of the SVG and if those don't exist, we default to 100.

We've had a few reports though of where SVGs are now showing up larger than expected. I've only been able to reproduce this issue if directly using wp_get_attachment_image to output an SVG, though curiously I'm getting the wrong size images on the previous release as well. It seems the bug with the new release has to do with adding srcset to these images, whereas previously those weren't being added as we were overriding height and width to be false. I don't think we need srcset, so this PR removes that from all SVGs.

On the previous release, if using wp_get_attachment_image and not setting a size (so defaulting to thumbnail) I get this markup:

<img src="http://oss.local/wp-content/uploads/2022/02/kiwi-2.svg" class="attachment-thumbnail size-thumbnail" alt="" loading="lazy" height="502.174" width="612">

This is incorrect as I should be getting an image that is 150x150, so I get a larger than expected image.

Using the same settings on the newest release:

<img width="150" height="150" src="http://oss.local/wp-content/uploads/2022/02/kiwi-2.svg" class="attachment-thumbnail size-thumbnail" alt="" loading="lazy" srcset="http://oss.local/wp-content/uploads/2022/02/kiwi-2.svg 150w, http://oss.local/wp-content/uploads/2022/02/kiwi-2.svg 300w, http://oss.local/wp-content/uploads/2022/02/kiwi-2.svg 1024w, http://oss.local/wp-content/uploads/2022/02/kiwi-2.svg 1536w, http://oss.local/wp-content/uploads/2022/02/kiwi-2.svg 2048w" sizes="(max-width: 150px) 100vw, 150px">

This gives me the right height and width set but because of the srcset, I can potentially get a larger or smaller image on various breakpoints.

After the changes in this PR:

<img width="150" height="150" src="http://oss.local/wp-content/uploads/2022/02/kiwi-2.svg" class="attachment-thumbnail size-thumbnail" alt="" loading="lazy">

Right height and width but no more srcset or sizes.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.

Changelog Entry

Fixed - Remove srcset and sizes from SVG image output

[dkotter]

This is now tackled in #44, so closing this out