Doc request: document empty conditionals

[matthewmueller]

Name	0 Filter	1 Filter	2 Filter
OR	return empty list	validate single filter	validate all filters
AND	return all items	validate single filter	validate all filters
NOT	return all items	validate single filter	validate all filters

Context: prisma/prisma#4784 (comment)

Perhaps on this page: https://www.prisma.io/docs/concepts/components/prisma-client/null-and-undefined

Details: https://www.notion.so/prismaio/Filter-condition-reduction-behavior-450c7baa5c5d4835a2c5dcc49c3eb494

[mhwelander]

• Suggest adding a section to prisma.io/docs/concepts/components/prisma-client/null-and-undefined about the effects of null on conditionals
• Suggest adding one example to each reference section (OR, AND, NOT) with a link to the general explanation: https://www.prisma.io/docs/reference/api-reference/prisma-client-reference#and