v0.15.6

What's Changed

• DOP-4207: use Gatsby Image to pre process images by @seungpark in #981
• DOP-4207: check if image exists before calling by @seungpark in #986
• DOP-4207: remove leading slash with regex by @seungpark in #988
• DOP-4264: allow sibling associated products' ToC to be visible by @seungpark in #985
• DOP-4287: Retry feedback submission after 401 errors by @rayangler in #987

Full Changelog: v0.15.4...v0.15.6