[PROPOSAL] Use JSON Schema

Add a new flag `--schema`

```console
pimo --schema file://schema.json
```

With regard to the [JSON Schema Specification](https://json-schema.org/), PIMO can

- enforce that every JSON Line in the input stream respect the schema (log an error and fail, or log a warning and skip if `--skip-line-on-error`)
- re-order fields in the output stream, in the same order they are defined in the schema

Some Go librairies that implement the JSON Schema specification : https://json-schema.org/implementations.html#validator-go

The issue proposes a new `--schema` CLI flag that accepts a `file://` JSON Schema. Start by locating the command-line option handling and reviewing the JSON Schema Specification and available Go libraries. Done means validating each JSON Line, honoring `--skip-line-on-error`, and ordering output fields as defined by the schema.

Written by the indexing model from the issue text.