add redirections

Author: BillWagner

.openpublishing.redirection.csharp.json

@@ -120,6 +120,14 @@
             "source_path_from_root": "/redirections/proposals/csharp-8.0/readonly-instance-members.md",
             "redirect_url": "/dotnet/csharp/language-reference/language-specification/structs#16411-properties"
         },
+        {
+            "source_path_from_root": "/redirections/proposals/csharp-8.0/null-coalescing-assignment.md",
+            "redirect_url": "/dotnet/csharp/language-reference/language-specification/expressions#1221-assignment-operators"
+        },
+        {
+            "source_path_from_root": "/redirections/proposals/csharp-8.0/async-streams.md",
+            "redirect_url": "/dotnet/csharp/language-reference/language-specification/statements.md#13953-await-foreach"
+        },
         {
             "source_path_from_root": "/redirections/proposals/csharp-9.0/nullable-reference-types-specification.md",
             "redirect_url": "/dotnet/csharp/language-reference/language-specification/types.md#893-nullable-reference-types"