docs(README): add sql-isolation-level in Usage

sashamelentyev · sashamelentyev · commit 7df93656c9b3 · 2022-09-01T14:25:08.000+03:00
diff --git a/README.md b/README.md
@@ -47,6 +47,8 @@ Flags:
         suggest the use of rpc.DefaultXXPath
   -source
         no effect (deprecated)
+  -sql-isolation-level
+        suggest the use of sql.LevelXX
   -tags string
         no effect (deprecated)
   -test
