Add core library and element classes for Basalt framework

src/elements/Frame.lua

@@ -0,0 +1,18 @@
+local Container = require("elements/Container")
+
+local Frame = setmetatable({}, Container)
+Frame.__index = Frame
+
+---@diagnostic disable-next-line: duplicate-set-field
+function Frame.new(id, basalt)
+    local self = setmetatable({}, Frame):__init()
+    self:init(id, basalt)
+    self.set("width", 12)
+    self.set("height", 6)
+    self.set("background", colors.blue)
+    self.set("type", "Frame")
+    self.set("z", 10)
+    return self
+end
+
+return Frame