You can see one design trend nowadays on many sites when images go outside content container.
This is how it looks
Now, you can do this in theme. When you add image in Gutenberg editor, just click on Align icon and choose Full width image or wide width
This will work also for content with Sidebar, however we recommend to use this feature only on Full width posts. You can enable full width in right side panel or simple disable sidebar globally in theme option – global enable/disable