Add wxDocManager::FindDocumentByPath() helper.

Simply refactor the code which already existed inside wxDocManager in a new
public method.

Closes #15126.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73730 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/docview.h

@@ -446,6 +446,9 @@ public:
     // Find template from document class info, may return NULL.
     wxDocTemplate* FindTemplate(const wxClassInfo* documentClassInfo);
 
+    // Find document from file name, may return NULL.
+    wxDocument* FindDocumentByPath(const wxString& path) const;
+
     wxDocument *GetCurrentDocument() const;
 
     void SetMaxDocsOpen(int n) { m_maxDocsOpen = n; }