docs: Fix Typo (typeorm#4412)

mharris717 · rustamwin · commit c8dbf099ba99 · 2019-07-10T18:17:31.000+05:00
diff --git a/docs/select-query-builder.md b/docs/select-query-builder.md
@@ -304,7 +304,7 @@ Which will produce:
 SELECT ... FROM users user WHERE user.name = 'Timber'
 ```
 
-You can add `AND` into an exist `WHERE` expression:
+You can add `AND` into an existing `WHERE` expression:
 
 ```typescript
 createQueryBuilder("user")
