Add block.json schema defintion to core blocks

[mkaz]

Description

Adds the schema defintion to the top of each core block to help development, in
supported editors the schema definition will show validation errors, offer
tooltips and autocomplete.

Schema definition:

"$schema": "https://json.schemastore.org/block.json",

How has this been tested?

• No functional change, confirm JSON format is still correct
• Added to documentation in Docs: Add section about using the schema during development #35835, see PR for example

Types of changes

Adds schema to top of each block.json file in core blocks. While going through and adding Prettier did format a couple of files so some minor whitespace, and array changes, nothing functional.

I did not correct any validation issues in this PR, I will create a new one with details on issues found by adding the schema. I'm not necessarily sure if the issues are with the schema definition or the block.json file.

[gziolo]

I think that this is a good direction that should help improve the experience for maintaining block.json files in the project. We should land this PR after the issues listed in #35902 get resolved to avoid confusion for those contributors who might see violations reported in their IDEs.

[mkaz]

We likely will want to wait on this merge as hopefully we can change it over to our own URLs based on this request:
https://make.wordpress.org/systems/2021/11/03/redirects-for-json-schemas/

[aristath]

I'm not familiar with SchemaStore... Out of curiosity, how is the schema maintained/updated there? 🤔

[mkaz]

@aristath Via GitHub PR at: https://github.com/SchemaStore/schemastore/blob/master/src/schemas/json/block.json

[fabiankaegy]

Looks good to me :)

[gziolo]

Opened #36351 as a follow-up to add a missing $schema field to a few more blocks. I also wrote integration tests to enforce that every block has block.json with the $schema field and the metadata validates against the local schema.