Tag Cloud: Add border block support

[akasunil]

What?

Add border block support to the Tag Cloud block.

Part of https://github.com/WordPress/gutenberg/issues/43247

Why?

Tag Cloud block is missing border support.

How?

Adds the border block support in block.json

Testing Instructions

• Add Tag Cloud block
• Apply the border
• Compare the result in the editor and front.

Screenshots or screencast

In backend:

In frontend: