Add some minimal styling to make block visible in editor.

[Marty O'Connor]

I noticed after creating a new block that at first it was nowhere to be found on the page. I think we should add some minimal styling to the block in the editor (outline, padding) to make it visible.

Suggestion:

In global.scss

.wp-block-post-content {
	@apply p-24;
	.wp-block {
		@apply p-4 outline outline-1 outline-primary-300;
	}
}

Before:

After

Here's a video screencast describing the problem:
https://www.loom.com/share/23da3e5304044453a560a64d7dd164bc?sid=1bf04088-98dd-479d-8e2c-a0563f5997bd

[Marty O'Connor]

See PR #21