Add examples to housing assistance documentation

Currently it's a one-person household in San Francisco. We can add:
* Married and number of kids, like the [MA income tax documentation](https://policyengine.github.io/openfisca-us//programs/states/ma/income-tax.html)
* Childcare expenses
* Elderly/disabled status
* Varying rent payments
* Whether the household is already enrolled
* When all the rules are implemented: microsimulation impacts (budgetary, poverty, inequality), need to consider take-up rates