Add support for full text search for PostgreSQL

[RobertCraigie]

https://www.prisma.io/docs/concepts/components/prisma-client/full-text-search

Suggested solution

Something like the following, search should be added to StringFilter and must be an instance of String.

Should be noted that I'm not stuck on String being the name.

# NOTE: actual API is still TODO
from prisma.querying import String

await client.post.find_first(
    where={
        'content': {
            'search': String.contains('cat', 'dog'),
        },
    },
)
await client.post.find_first(
    where={
        'content': {
            # for anything we don't explicitly support
            'search': String.raw('fox \| cat'),
        },
    },
)