updated briefings to be shown during spawn (#31)

fixes #26

Reviewed-on: #31
Co-authored-by: dutchie031 <timrorije@gmail.com>

src/classes/spearhead_events.lua

@@ -50,6 +50,19 @@ do
             table.insert(OnStageNumberChangedHandlers, handler)
         end
 
+        ---@class OnStageNumberChangeCompleteListener
+        ---@field OnStageNumberChangeComplete fun(self:OnStageNumberChangeCompleteListener, number:integer)
+        
+        local OnStageNumberChangeCompleteListeners = {}
+        ---@param listener OnStageNumberChangeCompleteListener
+        SpearheadEvents.AddStageNumberChangeCompleteListener = function(listener)
+            if type(listener) ~= "table" or type(listener.OnStageNumberChangeComplete) ~= "function" then
+                warn("Event handler not of type table/object with function OnStageNumberChangeComplete(self, number)")
+                return
+            end
+            table.insert(OnStageNumberChangeCompleteListeners, listener)
+        end
+
         ---@param newStageNumber number
         SpearheadEvents.PublishStageNumberChanged = function(newStageNumber)
             pcall(function ()
@@ -71,6 +84,16 @@ do
                     logError(err)
                 end
             end
+
+            for _, callable in pairs(OnStageNumberChangeCompleteListeners) do
+                local succ, err = pcall(function()
+                    callable:OnStageNumberChangeComplete(newStageNumber)
+                end)
+                if err then
+                    logError(err)
+                end
+            end
+
             Logger.new("Events", "INFO"):info("Published stage number changed to: " .. tostring(newStageNumber))
         end
     end