Term description: add spacing block supports

[ramonjd]

Related:

• Tracking: Addressing Design Tooling Consistency #43241
• Tracking: Dimensions Design Tools Consistency #43243

What?

Enabling spacing support for the Term description block

Why?

To create consistency across blocks.

How?

Adding the relevant block supports in block.json

Testing Instructions

1. Make sure you have some posts with tags or categories
2. Load the site editor and create / edit the archive template
3. Add a Term description block.
4. Confirm that the dimensions control panel is there
5. Add margin and padding.
6. Save and go to a term's archive page, e.g., http://localhost:8888/?tag=good-tag and confirm the styles appear on the frontend.
7. Test the new support works for the block via theme.json and global styles. See example JSON below.

	"styles": {
		"blocks": {
			"core/term-description": {
				"spacing": {
					"padding": "122px",
					"margin": "22px"
				}
			}
		}
	}

[apeatling]

✅ Confirm that the dimensions control panel is there
✅ Add margin and padding.
✅ Save and go to a term's archive page, e.g., http://localhost:8888/?tag=good-tag and confirm the styles appear on the frontend.
✅ Test the new support works for the block via theme.json and global styles. See example JSON below.