Tool to remove data-sizes and scrset from image elements in the post content

[jaspermdegroot]

Solution for #178

If there are posts that contain images with data-sizes and srcset attributes in the markup a menu page is added to the Tools menu and a warning message is shown on the dashboard and plugin menu page to point users to this page.

The plugin Tools menu page contains an explanation, a tool to automatically remove data-sizes and srcset from images, and instructions how to do this manually.

When all data-sizes and srcset are removed the Tools menu page and the warning message disappear.

[jaspermdegroot]

Still have to look into unit tests.

[damienroue]

Hi @jaspermdegroot. Have you found a way to remove srcset and sizes markup?

[jaspermdegroot]

Hi @damienroue

Yeah, this PR adds a tool to remove the attributes. It still needs to be reviewed by @joemcgill before we can merge and release a new version of the plugin with the tool. I also have to see why some tests failed on the last commit. Everything worked fine when I tested the code, but make sure you have a backup of your database if you decide to use it already!