Add KSY schema to SchemaStore
Kaitai has a schema in [its own repo](https://github.com/kaitai-io/ksy_schema)-- which is great! What'd be even more great is to automatically use it for code-completion in various IDEs, which involves keeping that schema up-to-date in the [SchemaStore](https://github.com/SchemaStore/schemastore) repo.

This can be set up manually from the kaitai repo today or by including the magic comment below in ksy files (only tested on VS Code), but it'd be awesome to get autocomplete "for free" by having a copy in their repo. 

```
# yaml-language-server: $schema=https://raw.githubusercontent.com/kaitai-io/ksy_schema/master/ksy_schema.json
```