Fix Rojo breaking when users undo/redo in Studio (#708)

plugin/src/Reconciler/applyPatch.lua

@@ -5,6 +5,8 @@
 	Patches can come from the server or be generated by the client.
 ]]
 
+local ChangeHistoryService = game:GetService("ChangeHistoryService")
+
 local Packages = script.Parent.Parent.Parent.Packages
 local Log = require(Packages.Log)
 
@@ -17,6 +19,8 @@ local reify = require(script.Parent.reify)
 local setProperty = require(script.Parent.setProperty)
 
 local function applyPatch(instanceMap, patch)
+	local patchTimestamp = DateTime.now():FormatLocalTime("LTS", "en-us")
+
 	-- Tracks any portions of the patch that could not be applied to the DOM.
 	local unappliedPatch = PatchSet.newEmpty()
 
@@ -199,6 +203,8 @@ local function applyPatch(instanceMap, patch)
 		end
 	end
 
+	ChangeHistoryService:SetWaypoint("Rojo: Patch " .. patchTimestamp)
+
 	return unappliedPatch
 end