v8.18.4

Changes since 8.18.3:

• heifload: raise security limits on references [caseywebdev]
• tiffload: squash out read errors in openin_source_read [aleens-labs]
• jxlsave: convert CMYK images to sRGB [DarthSim]
• heifload: fix -Winteger-overflow warning on 32-bit platforms [kleisauke]
• object: guard against non-input arguments [kleisauke]
• enumtypes: avoid misuse of G_GNUC_CONST for GCC 17 compat [kleisauke]

Windows binaries here:

https://github.com/libvips/build-win64-mxe/releases/tag/v8.18.4