Update Punctuator grammar

Author: leebyron

spec/Appendix B -- Grammar Summary.md

@@ -43,7 +43,7 @@ Token ::
 - FloatValue
 - StringValue
 
-Punctuator :: one of ! $ & ( ) ... : = @ [ ] { | } . [lookahead != .]
+Punctuator :: one of ! $ & ( ) ... : = @ [ ] { | } . [lookahead != {`.`, Digit}]
 
 Name ::
 

spec/Section 2 -- Language.md

@@ -176,7 +176,7 @@ and is {Ignored}.
 
 ### Punctuators
 
-Punctuator :: one of ! $ & ( ) ... : = @ [ ] { | } . [lookahead != .]
+Punctuator :: one of ! $ & ( ) ... : = @ [ ] { | } . [lookahead != {`.`, Digit}]
 
 GraphQL documents include punctuation in order to describe structure. GraphQL is
 a data description language and not a programming language, therefore GraphQL