Feature/mission refactor (#26)

* Refactored Mission classes to add Missions other than trigger zone missions. (eg. Runway Strikes, Resupply etc.)
* Runway strike initial POC
Co-authored-by: dutchie032 <dutchie032>

classes/_baseClasses/Queue.lua

@@ -0,0 +1,50 @@
+
+---@class Queue
+---@field private _items Array
+---@field private _first number
+---@field private _last number
+local Queue = {}
+Queue.__index = Queue
+
+---@return Queue
+function Queue.new()
+
+    local self = setmetatable({}, Queue)
+    self._items = {}
+    self._first = 1
+    self._last = 0
+    return self
+end
+
+---@return nil
+function Queue:push(item)
+    self._last = self._last + 1
+    self._items[self._last] = item
+end
+
+---@return any?
+function Queue:pop()
+    if self._first > self._last then
+        return nil
+    end
+
+    local item = self._items[self._first]
+    self._items[self._first] = nil
+    self._first = self._first + 1
+    return item
+end
+
+
+---@return Array<any>
+function Queue:toList()
+    local items = {}
+    for i = self._first, self._last do
+        items[#items + 1] = self._items[i]
+    end
+    return items
+end
+
+
+if Spearhead == nil then Spearhead = {} end
+if Spearhead._baseClasses == nil then Spearhead._baseClasses = {} end
+Spearhead._baseClasses.Queue = Queue