Introduce "recommended" validation rules (#4118)

Co-authored-by: enisdenjo <[email protected]>
Co-authored-by: enisdenjo <[email protected]>

Author: benjie

src/index.ts

@@ -355,6 +355,7 @@ export {
   ValidationContext,
   // All validation rules in the GraphQL Specification.
   specifiedRules,
+  recommendedRules,
   // Individual validation rules.
   ExecutableDefinitionsRule,
   FieldsOnCorrectTypeRule,
@@ -382,6 +383,7 @@ export {
   ValuesOfCorrectTypeRule,
   VariablesAreInputTypesRule,
   VariablesInAllowedPositionRule,
+  MaxIntrospectionDepthRule,
   // SDL-specific validation rules
   LoneSchemaDefinitionRule,
   UniqueOperationTypesRule,