Required not adding as attribute

[braingu-matt]

https://github.com/benedwards44/schemalister/blob/29bb3eae662df21b780b42c78d72a48cf2664c26/getschema/tasks.py#L227

I believe this line should check for nillable rather than required per https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_fields_describe.htm#apex_methods_system_fields_describe

I'm finding that no field is ever marked as Required