Add PNG source file detection in `make-favicon.js` so the script can
use either `favicon.svg` or `favicon.png` as input. Previously, only
SVG was supported, causing failures when no SVG was present.
- Introduce `detectSourceFile()` to check for SVG first, then PNG
- Rename variables to avoid shadowing (`pngPath` → `outPath`, loop var)
- Log detected source type for better visibility during generation
- Update generated `favicon.ico` accordingly
hykocx