// Function: Border
// - @argument: $border-colorm $border-size(default is 1px), $border-style(default is 'solid')
// - @returns 'border values according to @arguments
// - use cases:
// - defining a border without specifying default values
// - passing semantic values as @arguments
@function border($border-color, $border-size:1px, $border-style:solid){
@return #{$border-size} #{$border-style} #{$border-color};
}