Meta Decorator

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## Motivation

I often have lots of small schemas containing unique `Meta` classes with only a few attributes. The `Meta` class sometimes requires more lines than the schema definition and makes a file containing multiple schemas harder to read. This is especially true when using `marshmallow-jsonapi` due to `type_`.

## Proposal

Provide a `meta` decorator that will inject its kwargs into a `Meta` class for the class it is wrapping.

## Example

Before:

```py
class TestSchema(Schema):
foo = fields.String()
bar = fields.String()

class Meta:
type_ = 'tests'
ordered = True
```

After:

```py
@meta(type_='tests', ordered=True)
class TestSchema(Schema):
foo = fields.String()
bar = fields.String()
```

Start by reviewing how Schema classes handle their nested Meta class and compare that behavior with the proposed @meta(type_='tests', ordered=True) usage. Confirm how decorator arguments should become Meta attributes, including the marshmallow-jsonapi type_ case. Done means the decorator works for the shown schema pattern and preserves the existing Meta behavior.

Written by the indexing model from the issue text.