Add settings.execMaxBufferSize to control buffer size of exec node (#2819)

Co-authored-by: Dave Conway-Jones <dceejay@users.noreply.github.com>
closes #2817

packages/node_modules/node-red/settings.js

@@ -41,6 +41,10 @@ module.exports = {
     // Timeout in milliseconds for HTTP request connections
     //  defaults to 120 seconds
     //httpRequestTimeout: 120000,
+    
+    // Maximum buffer size for the exec node
+    //  defaults to 10Mb
+    //execMaxBufferSize: 10000000,
 
     // The maximum length, in characters, of any message sent to the debug sidebar tab
     debugMaxLength: 1000,