This is Unity's legacy Sun Shaft post processing effect, modified to work with Unity's Post Processing Stack. Tested using the Standard Rendering Pipeline. Updated to also be visible in the editor.
Simply add the entire folder into your Assets folder.
Add the SunShafts script/component to the Main Camera. You can use the editor only toggle 'Sync With Editor Camera?' in order to enable syncing between the current camera and the editor camera (useful for when you have multiple cameras using SunShafts, in order to stop multiple cameras fighting to sync with the editor camera).