Add anytools formatter/validator to Online tools

[D0bby999]

Adds a free, client-side formatter/validator to Online tools.

Followed the contributing guidelines:

• * bullet with the [name](url) - description. shape
• description does not mention JSON (implied by the list)
• ends with a dot, no trailing whitespace
• searched the section first — the closest existing entries (JSONLint, JSONMaster, Collapsible JSON Formatter) are separate tools

Everything runs in the browser with no upload and no signup; JSON5 mode accepts comments and trailing commas.

Disclosure: I maintain anytools.world.