Add substitutePlaceholders to mcp export for the Audits Issues needs

Bug: None
Change-Id: Ief21092d8e9f907f57889fc0f5f13bc33aaa1977
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/7177942
Reviewed-by: Alex Rudenko <[email protected]>
Commit-Queue: Natallia Harshunova <[email protected]>

Author: Natallia Harshunova

mcp/mcp.ts

@@ -31,6 +31,6 @@ export {
   type EventTypes as IssuesManagerEventTypes,
   IssuesManager
 } from '../front_end/models/issues_manager/IssuesManager.js';
-export {findTitleFromMarkdownAst} from '../front_end/models/issues_manager/MarkdownIssueDescription.js';
+export * as MarkdownIssueDescription from '../front_end/models/issues_manager/MarkdownIssueDescription.js';
 export * as TraceEngine from '../front_end/models/trace/trace.js';
 export * as Marked from '../front_end/third_party/marked/marked.js';