Add lat and lng atts to image-map shortcode

[AK-digital]

Hi there,

I'd like to add my little contribution to this cool plugin : my changes will allow editor to use lat="" and lng="" to the image-map shortcode, redefining the center point on first load if atts are set (''0' if not.)

My first official contribution to the community. Hope it will be published =)

Cheers !

[AK-digital]

Limit input lat and lng to int