Add middleware to loader to show "broken" icon when import from boxel.ai icons fails #7828

All 720 tests pass, 2 skipped in 20m 46s

    1 files ±0     1 suites ±0 20m 46s ⏱️ -33s
722 tests ±0 720 ✔️ ±0 2 💤 ±0 0 ❌ ±0
727 runs ±0 725 ✔️ ±0 2 💤 ±0 0 ❌ ±0

Results for commit 41b7164. ± Comparison against earlier commit 0004d58.