Don't drop repeatable keyword when formatting directive (#256)

Author: tadeokondrak

formatter/formatter.go

@@ -360,6 +360,10 @@ func (f *formatter) FormatDirectiveDefinition(def *ast.DirectiveDefinition) {
 		f.FormatArgumentDefinitionList(def.Arguments)
 	}
 
+	if def.IsRepeatable {
+		f.WriteWord("repeatable")
+	}
+
 	if len(def.Locations) != 0 {
 		f.WriteWord("on")
 

formatter/testdata/baseline/FormatSchema/directive.graphql

@@ -1 +1,2 @@
+directive @bar repeatable on FIELD | OBJECT
 directive @foo on FIELD | OBJECT

formatter/testdata/baseline/FormatSchemaDocument/directive.graphql

@@ -1 +1,2 @@
 directive @foo on FIELD | OBJECT
+directive @bar repeatable on FIELD | OBJECT

formatter/testdata/source/schema/directive.graphql

@@ -1 +1,2 @@
 directive @foo on FIELD|OBJECT
+directive @bar repeatable on FIELD|OBJECT