Up-to-date STM32F1 README (#14386)

Marlin/src/HAL/HAL_STM32F1/README.md

-# This HAL is for STM32F103 boards used with libmaple/stm32duino Arduino core.
+# STM32F1
 
-# This HAL is in development. Currently has been tested in Malyan M200 (103CBT6), Chitu 3d (103ZET6), and custom boards(103VET6).
+This HAL is for STM32F103 boards used with [Arduino STM32](https://github.com/rogerclarkmelbourne/Arduino_STM32) framework.
 
-### The stm32 core needs a modification in the file util.h to avoid conflict with Marlin macros for Debug.
-Since only 1 file needs change in the stm32duino core, it's preferable over making changes to Marlin.
-
-
-After these lines:
-<>
-#else
-#define ASSERT_FAULT(exp) (void)((0))
-#endif
-<>
+Currently has been tested in Malyan M200 (103CBT6), SKRmini (103RCT6), Chitu 3d (103ZET6), and various 103VET6 boards.
 
 ### Main developers:
-Victorpv
-xC000005
-
-
-### Most up to date repository for this HAL:
-https://github.com/victorpv/Marlin/tree/bugfix-2.0.x
-
-PRs should only be sent to Marlin bugfix-2.0.x branch once tested in printing so not to introduce new bugs.
-For testing/dev, you can submit to the above branch
+- Victorpv
+- xC000005
+- thisiskeithb
+- tpruvot