Added firmware endpoint

Necessary to handle the request and response of the firmware API endpoint.

lib/trmnl/api/endpoints/firmware.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require "pipeable"
+
+module TRMNL
+  module API
+    module Endpoints
+      # Handles API request/response.
+      class Firmware
+        include Dependencies[:client, contract: "contracts.firmware", model: "models.firmware"]
+        include Pipeable
+
+        def call
+          pipe client.get("firmware/latest"),
+               try(:parse, catch: JSON::ParserError),
+               validate(contract, as: :to_h),
+               to(model, :for)
+        end
+      end
+    end
+  end
+end