JSON Schema Draft07 ->Draft2019

Hi everyone,

### Problem Statement 🛑

1. I've used the code example, which works as expected. But if I use `migrate.draft2019` from your example, no `$schema` is set. Is this expected behavior?

2. Another problem would be, that I need to migrate a lot of `draft07` to at least `draft2019`. But I guess your are only handling `draft-04` to newer ones?

### What I have tried 🛠

1. used `ajv-cli migrate`
2. wrote own `nodejs` code using your `json-schema-migrate`.

#### Behavior
- No changes in `$id` fields (e.g. removing `#` and `/`).
- No update of `$schema` field.

### Wishes 🎁
- migrate from `draft07` to `draft2019`

I'm not an JSON Schema expert, so I'm really not sure if this all is expected behavior or not.

Kind regards,
Daniel