Add arc60

[Vertex-kb]

Description

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[sigprof]

@Vertex-kb
Some people in the QMK Discord reported that the Vertex Arc60 PCB they received has a different bootloader — instead of stm32duino, which is specified in this PR, the board actually has an UF2 bootloader based on https://github.com/mmoskal/uf2-stm32f103, therefore compiling the current vertex/arc60 code in QMK does not produce a suitable firmware for that PCB.

Apparently making this change to the current vertex/arc60 code produces a firmware which works on the Vertex Arc60 PCB with the UF2 bootloader:

diff --git a/keyboards/vertex/arc60/info.json b/keyboards/vertex/arc60/info.json
index bfb8e4fc3a..ee4bdf60be 100644
--- a/keyboards/vertex/arc60/info.json
+++ b/keyboards/vertex/arc60/info.json
@@ -13,7 +13,8 @@
         "on_state": 0
     },
     "processor": "STM32F103",
-    "bootloader": "stm32duino",
+    "board": "STM32_F103_STM32DUINO",
+    "bootloader": "uf2boot",
     "community_layouts": [
         "60_ansi",
         "60_ansi_split_bs_rshift",

Would you please clarify the bootloader situation with Arc60? Do any PCBs with the stm32duino bootloader exist in the wild, or was the bootloader replaced with UF2 before the final PCBs were made and shipped? Depending on that, either another PCB revision should be added to the vertex/arc60 code, or the existing code should be updated to use the uf2boot bootloader.

Also I suppose that the vertex/arc60h board would have the same problem.