Improve 11.5 image compression
Reduce color depth of the three largest 11.5 release post images and run through zopflipng.
| filename | original size | new size | savings |
|---|---|---|---|
| source/images/11_5/board-card-design.png | 157KB | 45KB | 71% |
| source/images/11_5/discussion-activity-design.png | 264KB | 94KB | 58% |
| source/images/11_5/knative.png | 471KB | 111KB | 76% |
Total savings: 642KB
Edited by James Ramsay (ex-GitLab)