Add directpins 21 keys pico (#24919)

* Add directpins 21 keys pico
- https://learn.adafruit.com/diy-pico-mechanical-keyboard-with-fritzing-circuitpython/21-key-pico-keyboard

* Rename from 21keys to pico_pad

* Add pico_pad readme

* Update bootloader instruction

---------

Co-authored-by: Dai <dai@ovacoda.com>

keyboards/adafruit/pico_pad/keyboard.json

@@ -0,0 +1,53 @@
+{
+    "manufacturer": "Raspberry Pi",
+    "keyboard_name": "DirectPins Pico Pad 21 keys RP2040",
+    "maintainer": "icyavocado",
+    "bootloader": "rp2040",
+    "usb": {
+        "vid": "0x2326",
+        "pid": "0xFEED",
+        "device_version": "0.0.1"
+    },
+    "features": {
+        "bootmagic": true,
+        "mousekey": true,
+        "extrakey": true
+    },
+    "processor": "RP2040",
+    "matrix_pins": {
+        "direct": [
+            [ "GP0",  "GP1",  "GP2",  "GP3",   "GP4",   "GP5",   "GP6" ],
+            [ "GP7",  "GP8",  "GP9",  "GP10",  "GP11",  "GP12",  "GP13"],
+            [ "GP14", "GP16", "GP17", "GP18",  "GP19",  "GP20",  "GP21"]
+        ]
+    },
+    "layouts": {
+        "LAYOUT": {
+            "layout": [
+                {"label": "GP0", "x": 0, "y": 0, "matrix": [0, 0]},
+                {"label": "GP1", "x": 0, "y": 1, "matrix": [0, 1]},
+                {"label": "GP2", "x": 0, "y": 2, "matrix": [0, 2]},
+                {"label": "GP3", "x": 0, "y": 3, "matrix": [0, 3]},
+                {"label": "GP4", "x": 0, "y": 4, "matrix": [0, 4]},
+                {"label": "GP5", "x": 0, "y": 5, "matrix": [0, 5]},
+                {"label": "GP6", "x": 0, "y": 6, "matrix": [0, 6]},
+
+                {"label": "GP7", "x": 1, "y": 0, "matrix": [1, 0]},
+                {"label": "GP8", "x": 1, "y": 1, "matrix": [1, 1]},
+                {"label": "GP9", "x": 1, "y": 2, "matrix": [1, 2]},
+                {"label": "GP10", "x": 1, "y": 3, "matrix": [1, 3]},
+                {"label": "GP11", "x": 1, "y": 4, "matrix": [1, 4]},
+                {"label": "GP12", "x": 1, "y": 5, "matrix": [1, 5]},
+                {"label": "GP13", "x": 1, "y": 6, "matrix": [1, 6]},
+
+                {"label": "GP14", "x": 2, "y": 0, "matrix": [2, 0]},
+                {"label": "GP16", "x": 2, "y": 1, "matrix": [2, 1]},
+                {"label": "GP17", "x": 2, "y": 2, "matrix": [2, 2]},
+                {"label": "GP18", "x": 2, "y": 3, "matrix": [2, 3]},
+                {"label": "GP19", "x": 2, "y": 4, "matrix": [2, 4]},
+                {"label": "GP20", "x": 2, "y": 5, "matrix": [2, 5]},
+                {"label": "GP21", "x": 2, "y": 6, "matrix": [2, 6]}
+            ]
+        }
+    }
+}

keyboards/adafruit/pico_pad/keymaps/default/keymap.json

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+{
+    "keyboard": "adafruit/pico_pad",
+    "keymap": "default",
+    "layout": "LAYOUT",
+    "layers": [
+        [
+            "KC_A", "KC_B", "KC_C", "KC_D", "KC_E", "KC_F", "KC_G",
+            "KC_H", "KC_I", "KC_J", "KC_K", "KC_L", "KC_M", "KC_N",
+            "KC_O", "KC_P", "KC_Q", "KC_R", "KC_S", "KC_T", "KC_U"
+        ]
+    ]
+}

keyboards/adafruit/pico_pad/readme.md

@@ -0,0 +1,25 @@
+# PICO PAD
+
+![PICO PAD](https://imgur.com/Nl4tZPl.jpg)
+
+A RP2040 powered direct pins QMK keyboard in 3x7 layout.
+
+A guide can be found here: [Pico Mechanical Keyboard](https://learn.adafruit.com/diy-pico-mechanical-keyboard-with-fritzing-circuitpython/overview)
+
+* Keyboard Maintainer: [IcyAvocado](https://github.com/icyavocado)
+* Hardware Supported: [Pico 1 Microcontrollers - RP2040](https://www.raspberrypi.com/documentation/microcontrollers/pico-series.html#pico-1-family)
+* Hardware Availability: [The PiHut](https://thepihut.com/products/raspberry-pi-pico) | [Adafruit Parts](https://learn.adafruit.com/diy-pico-mechanical-keyboard-with-fritzing-circuitpython/overview)
+
+Make example for this board (after setting up your build environment):
+
+```sh
+qmk compile -kb adafruit/pico_pad -km default
+```
+
+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).
+
+## Bootloader
+
+Enter the bootloader:
+* **Physical reset button**: Briefly press the reset button on the left of the PCB - some may have pads you must short instead
+* **Boot button**: Press and hold the BOOTSEL button on the pico when powered on