refactor(boards): Add metadata for boards.

* Standalone and pro-micro format board metadata added.

app/boards/arm/bdn9/bdn9_rev2.yml

@@ -0,0 +1,11 @@
+file_format: "1"
+id: bdn9_rev2
+name: BDN9 Rev2
+type: board
+arch: arm
+features:
+  - keys
+  - encoder
+outputs:
+  - usb
+url: https://keeb.io/products/bdn9-rev-2-3x3-9-key-macropad-rotary-encoder-and-rgb

app/boards/arm/bluemicro840/bluemicro840_v1.zmk.yml

@@ -0,0 +1,10 @@
+file_format: "1"
+id: bluemicro840_v1
+name: BlueMicro840 v1
+type: board
+arch: arm
+outputs:
+  - usb
+  - ble
+url: https://nrf52.jpconstantineau.com/docs/bluemicro840_v1/
+exposes: [pro_micro]

app/boards/arm/nice60/nice60.zmk.yml

@@ -0,0 +1,12 @@
+file_format: "1"
+id: nice60
+name: nice!60
+type: board
+arch: arm
+features:
+  - keys
+  - underglow
+outputs:
+  - usb
+  - ble
+url: https://nicekeyboards.com/nice-60

app/boards/arm/nice_nano/nice_nano.zmk.yml

@@ -0,0 +1,10 @@
+file_format: "1"
+id: nice_nano
+name: nice!nano v1
+type: board
+arch: arm
+outputs:
+  - usb
+  - ble
+url: https://nicekeyboards.com/nice-nano
+exposes: [pro_micro]

app/boards/arm/nice_nano/nice_nano_v2.zmk.yml

@@ -0,0 +1,10 @@
+file_format: "1"
+id: nice_nano_v2
+name: nice!nano v2
+type: board
+arch: arm
+outputs:
+  - usb
+  - ble
+url: https://nicekeyboards.com/nice-nano
+exposes: [pro_micro]

app/boards/arm/planck/planck_rev6.zmk.yml

@@ -0,0 +1,10 @@
+file_format: "1"
+id: planck_rev6
+name: Planck Rev6
+type: board
+arch: arm
+features:
+  - keys
+outputs:
+  - usb
+url: https://olkb.com/collections/planck

app/boards/arm/proton_c/proton_c.zmk.yml

@@ -0,0 +1,9 @@
+file_format: "1"
+id: proton_c
+name: QMK Proton-C
+type: board
+arch: arm
+outputs:
+  - usb
+url: https://qmk.fm/proton-c/
+exposes: [pro_micro]