Add example json volumetrics

[berland]

The table in the json file in this PR can be parsed into a DataFrame like this:

from pathlib import Path
import json
import pandas as pd
js = json.loads(Path('1_geogrid_vol_oil_1.json').read_text())
df = pd.DataFrame.from_records(js["table"]["data"], columns=js["table"]["columns"])

This PR is an example, and not for merging.

[jcrivenaes]

What is the use case?

[berland]

What is the use case?

This is a potentially way-too-late suggestion for Emerson on how to export RMS volumetrics and other data, as both txt files and xlsx export of different RMS-data requires writing dedicated parsers.