Add controller docs (mostly just placeholder)

docs/device/update_controller.md

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+# Update controller
+
+**Under Construction:** This section will be populated when these devices are released.
+
+This page will document equipments needed to use the `miniscope_io.device_update` module (or `mio update` interface.) 
+## prerequisite
+- A custom FTDI chip based IR transmitter (details will be released soon)