Add concat operator to standard sql.

Author: vertical-blank

src/main/java/com/github/vertical_blank/sqlformatter/languages/StandardSqlFormatter.java

@@ -379,6 +379,7 @@ public DialectConfig dialectConfig() {
         .indexedPlaceholderTypes(Collections.singletonList("?"))
         .namedPlaceholderTypes(Collections.emptyList())
         .lineCommentTypes(Arrays.asList("--"))
+        .operators(Collections.singletonList("||"))
         .build();
   }