added charting for inequality metrics

[masterismail]

usage

# Import necessary modules
from policyengine import EconomicImpact

# Create an instance of EconomicImpact
impact = EconomicImpact(
    reform={"gov.hmrc.income_tax.rates.uk[0].rate": {"2024-01-01.2100-12-31": 0.55}}, 
    country="uk"
)

fig_all = impact.chart("inequality")


fig_all.show()

output

inequality all