Invisible tummy time mat default replacement

This mod will replace your current blue and pink plaid tummy time mat with an invisible one. That way you can place your own mat manually underneath your infants or just keep them on the ground without a mat. This was requested by simmers on the forums who were disappointed  that they were unable to change the tummy time mat swatches and that it was the same mat used for all infants. Please do remember that this is a default replacement, so all tummy time mats in both new and old saves will become invisible once this is in your mods folder.