DOC: Add example with ``numpy_nullable`` to ``pd.read_json()``
- [x] [closes](https://github.com/noatamir/pyladies-berlin-sprints/issues/4)
Is this related to my changes?
```
Traceback (most recent call last):
  File "/home/runner/work/pandas/pandas/doc/make.py", line 392, in <module>
    sys.exit(main())
  File "/home/runner/work/pandas/pandas/doc/make.py", line 373, in main
    globals()["pandas"] = importlib.import_module("pandas")
  File "/home/runner/micromamba/envs/test/lib/python3.10/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/home/runner/work/pandas/pandas/pandas/__init__.py", line 138, in <module>
    from pandas import api, arrays, errors, io, plotting, tseries
  File "/home/runner/work/pandas/pandas/pandas/api/__init__.py", line 2, in <module>
    from pandas.api import (
  File "/home/runner/work/pandas/pandas/pandas/api/typing/__init__.py", line 31, in <module>
    from pandas.io.json._json import JsonReader
  File "/home/runner/work/pandas/pandas/pandas/io/json/__init__.py", line 1, in <module>
    from pandas.io.json._json import (
  File "/home/runner/work/pandas/pandas/pandas/io/json/_json.py", line 508, in <module>
    def read_json(
  File "/home/runner/work/pandas/pandas/pandas/util/_decorators.py", line 379, in decorator
    params_applied = [
  File "/home/runner/work/pandas/pandas/pandas/util/_decorators.py", line 380, in <listcomp>
    component.format(**params)
KeyError: '"index"'
``` @mroeschke can you help me here?
When I do this the do this I get no error when I import pandas from pandas-dev env.
```
>>> data = '{{"index":{{"0":0,"1":1}},"a":{{"0":1,"1":null}},' \
    ...        '"b":{{"0":2.5,"1":4.5}},"c":{{"0":true,"1":false}},' \
    ...        '"d":{{"0":"a","1":"b"}},"e":{{"0":1577.2,"1":1577.1}}}}'
    >>> df = pd.read_json(data, dtype_backend="numpy_nullable")
    >>> print(df)
       index     a    b      c  d       e
    0      0     1  2.5   True  a  1577.2
    1      1  <NA>  4.5  False  b  1577.1
```
But I get: ``ValueError: Key name of object must be 'string' when decoding 'object'``. When the example is
```
>>> data = '{"index": {"0": 0, "1": 1}, ' \
    ...        '"a": {"0": 1, "1": null}, ' \
    ...        '"b": {"0": 2.5, "1": 4.5}, ' \
    ...        '"c": {"0": true, "1": false}, ' \
    ...        '"d": {"0": "a", "1": "b"}, ' \
    ...        '"e": {"0": 1577.2, "1": 1577.1}}'
    >>> df = pd.read_json(data, dtype_backend="numpy_nullable")
    >>> print(df)
       index     a    b      c  d       e
    0      0     1  2.5   True  a  1577.2
    1      1  <NA>  4.5  False  b  1577.1
```
This happens:
```
>>> import pandas as pd
+ /Users/linussommer/miniforge3/envs/pandas-dev/bin/ninja
[1/1] Generating write_version_file with a custom command
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/linussommer/Documents/GitHub/pandas-linus-md/pandas/__init__.py", line 138, in <module>
    from pandas import api, arrays, errors, io, plotting, tseries
  File "/Users/linussommer/Documents/GitHub/pandas-linus-md/pandas/api/__init__.py", line 2, in <module>
    from pandas.api import (
  File "/Users/linussommer/Documents/GitHub/pandas-linus-md/pandas/api/typing/__init__.py", line 31, in <module>
    from pandas.io.json._json import JsonReader
  File "/Users/linussommer/Documents/GitHub/pandas-linus-md/pandas/io/json/__init__.py", line 1, in <module>
    from pandas.io.json._json import (
  File "/Users/linussommer/Documents/GitHub/pandas-linus-md/pandas/io/json/_json.py", line 508, in <module>
    def read_json(
  File "/Users/linussommer/Documents/GitHub/pandas-linus-md/pandas/util/_decorators.py", line 379, in decorator
    params_applied = [
  File "/Users/linussommer/Documents/GitHub/pandas-linus-md/pandas/util/_decorators.py", line 380, in <listcomp>
    component.format(**params)
KeyError: '"index"'
```
even though the code runs otherwise.
