Fix a parser bug to parse '1' as IntLit

Signed-off-by: Danila Fedorin <danila.fedorin@gmail.com>

src/Bergamot/Parser.elm

@@ -47,7 +47,7 @@ strLit =
 
 name : Parser String
 name = Parser.variable
-    { start = \c -> Char.isAlphaNum c || c == '_'
+    { start = \c -> Char.isAlpha c || c == '_'
     , inner = \c -> Char.isAlphaNum c || c == '_'
     , reserved = Set.empty
     }