Add Iron160 I160-S and I160-H PCBs support (#20077)

Co-authored-by: Ryan <fauxpark@gmail.com>
Co-authored-by: jack <0x6a73@protonmail.com>

keyboards/smithrune/iron160/readme.md

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+# Iron 160 QMK folder
+
+![Iron160](https://i.imgur.com/8B2l2pnh.jpg)
+
+## Introduction
+
+This is the QMK Firmware repository for the Iron160 PCB, a keyboard designed by [Smith and Rune](https://smithrune.com/) and PCB designed by [Gondolindrim](http://github.com/Gondolindrim), who is also the firwmare maintainer.
+
+There are two variants of the PCB: a solderable (I160-S) and a hotswap (I160-H) PCB. Both support a myriad of alternative layouts, as well as RGB LEDs for underglow light.
+
+## How to flash
+
+### Enter bootloader
+
+The DFU state in the bootloader can be accessed in 3 ways:
+
+* **Bootmagic reset**: Hold down the key at (0,0) in the matrix (usually the top left key, escape in the default keymap) and plug in the keyboard;
+* **Physical reset button**: press the button on the front of the PCB, next to caps lock, for at least five seconds;
+* **Keycode in layout**: Press the key mapped to `QK_BOOT`; in the default layout, that is top left key ('escape') in layer 1.
+
+### How to compile and flash
+
+After checking what PCB you own and setting up your build environment, you can compile the Iron 165R2 default keymap by using one of the options below.
+
+    make smithrune/iron160/iron160_s:default
+    make smithrune/iron160/iron160_h:default
+
+And use dfu-util in the command line or through a GUI like QMK toolbox to upload the firmware to the PCB. To directly flash the PCB after it is put into a DFU state, use:
+
+
+    make smithrune/iron160/iron160_s:default:flash
+    make smithrune/iron160/iron160_h:default:flash
+
+See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).