feat: add batch()

src/__tests__/batch.spec.luau

@@ -0,0 +1,38 @@
+local atom = require(script.Parent.Parent.atom)
+local batch = require(script.Parent.Parent.batch)
+local effect = require(script.Parent.Parent.effect)
+local subscribe = require(script.Parent.Parent.subscribe)
+
+return function()
+	it("batches updates", function()
+		local source = atom(1)
+		local value = 0
+		subscribe(source, function()
+			value += 1
+		end)
+		batch(function()
+			source(2)
+			source(3)
+			source(4)
+		end)
+		expect(value).to.equal(1)
+	end)
+
+	it("handles duplicate listeners", function()
+		local a = atom(1)
+		local b = atom(1)
+		local value = 0
+		effect(function()
+			value += 1
+			a()
+			b()
+		end)
+		value = 0 -- effect() will run once initially
+		batch(function()
+			a(2)
+			b(2)
+			a(3)
+		end)
+		expect(value).to.equal(1)
+	end)
+end