Update changelog for `v6.6.0`
Update changelog for `v6.6.0`

faceair/nativefier-slack,gfpacheco/Nativefier,gfpacheco/Nativefier,pixel9/nativefier,faceair/nativefier-slack,zucher/nativefier,pixel9/nativefier,zucher/nativefier,gfpacheco/Nativefier,skewedlines/Nativefier,jiahaog/Nativefier,pixel9/nativefier,zucher/nativefier,jiahaog/Nativefier,skewedlines/Nativefier,jiahaog/Nativefier,skewedlines/Nativefier