Add middleware to loader to show "broken" icon when import from boxel.ai icons fails #7807

All 720 tests pass, 2 skipped in 20m 30s

    1 files ±0     1 suites ±0 20m 30s ⏱️ -50s
722 tests ±0 720 ✔️ +1 2 💤 ±0 0 ❌ ±0
727 runs ±0 725 ✔️ +2 2 💤 ±0 0 ❌ - 1

Results for commit 1a85f3a. ± Comparison against earlier commit 572a16c.