Those who have installed mods for GTA 5 may have used a tool named Script Hook V for the same at some point.

You can see it in action with the video below from YouTube outlet GTA Series Videos. The grappling hook was scripted by JulioNIB and is used in conjunction with the Script Hook V .asi loader.

Installation is fairly simple, you need the latest version of ScriptHookV.dll, Asi Loader (Bundled with Script Hook) and the mod files (.asi).