feat: Add support for custom scalar validation (#3376)

* fix: VariableJSONSchema optional input types
* support custom schemas in monaco-graphql
* improve descriptions

Author: bboure

.changeset/few-hats-move.md

@@ -0,0 +1,5 @@
+---
+'graphql-language-service': patch
+---
+
+Fix Variables JSON Schema for null values

.changeset/tame-lions-teach.md

@@ -0,0 +1,6 @@
+---
+'graphql-language-service': minor
+'monaco-graphql': minor
+---
+
+Add support for custom scalars

packages/graphql-language-service/src/utils/__tests__/__schema__/StarWarsSchema.graphql

@@ -4,6 +4,28 @@ schema {
 
 directive @test(testArg: Boolean!) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT
 
+scalar SomeCustomScalar
+scalar EmailAddress
+scalar Even
+scalar SpecialScalar
+scalar SpecialDate
+scalar FooBar
+scalar Foo
+
+"""
+An input type with custom scalars
+"""
+input CustomScalarsInput {
+  """
+  example email
+  """
+  email: EmailAddress
+  """
+  example even
+  """
+  even: Even
+}
+
 enum Episode {
   NEWHOPE
   EMPIRE