fix: include missing boolean type in JSONValue union (#373)

Author: thebearingedge

types/index.d.ts

@@ -477,6 +477,7 @@ declare namespace postgres {
     | null
     | string
     | number
+    | boolean
     | Date // serialized as `string`
     | readonly JSONValue[]
     | { toJSON(): any } // `toJSON` called by `JSON.stringify`; not typing the return type, typings is strict enough anyway