Add user preference to the protocol.

src/server/protocol.ts

@@ -3007,6 +3007,12 @@ namespace ts.server.protocol {
          * For those entries, The `insertText` and `replacementSpan` properties will be set to change from `.x` property access to `["x"]`.
          */
         readonly includeCompletionsWithInsertText?: boolean;
+        /**
+         * Unless this option is disabled, or `includeCompletionsWithInsertText` is not enabled,
+         * member completion lists triggered with `.` will include entries on potentially-null and potentially-undefined
+         * values, with insertion text to replace preceding `.` tokens with `?.`.
+         */
+        readonly includeAutomaticOptionalChainCompletions?: boolean;
         readonly importModuleSpecifierPreference?: "relative" | "non-relative";
         readonly allowTextChangesInNewFiles?: boolean;
         readonly lazyConfiguredProjectsFromExternalProject?: boolean;