Incorporate postgraphile-tag-json-tools

### Feature description

@phryneas has written https://github.com/mayflower/postgraphile-tag-json-tools which enables more accurate JSON schema for the postgraphile.tags.jsonc file, leading to better auto-complete (and hopefully detection of misconfiguration, e.g. typos in references, invalid tags, etc).

### Breaking changes

Potentially more esoteric tags won't be supported.

Start by reviewing how postgraphile.tags.jsonc is currently handled and then read the linked postgraphile-tag-json-tools project to understand its integration points. Check which tags the starter currently supports and verify that the resulting schema provides the intended autocomplete and configuration validation without silently omitting required tags.

Written by the indexing model from the issue text.