add padding to grid code example

Example: css padding in grid

/* HTML */
<div class="grid">
	<div class="grid-item">
	<div class="grid-item">
	<div class="grid-item">
</div>

<style>
/* CSS */
	.grid {
		display: grid;
		grid-template-columns: 1fr 1fr;
		column-gap: 20px; /* this will put a gap of 20px between the columns of the grid */
	}
</style>