doxygen: add documentation for doxygen #5211

Job	Run time
RT-Thread Online Packages (STM32F407 RT-Spark)	5m 17s
RTduino/Arduino Libraries (STM32F412 Nucleo)	9m 38s
RTduino/Arduino Libraries (Raspberry Pico)	10m 11s
others_at32_hc32_ht32	5m 13s
stm32l4_f0_f1	11m 37s
stm32_f2_f4	7m 27s
stm32_f7_g0_h7_mp15_u5_h5_wb5	3m 50s
nxp_renesas	4m 6s
nuvoton	3m 35s
gd32_n32_apm32	3m 22s
Infineon_TI_microchip	4m 42s
mips	1m 3s
aarch64	2m 42s
riscv-none	1m 19s
riscv64-unknown	1m 43s
hpmicro	1m 4s
llvm-arm	4m 24s
simulator	52s
ESP32C3	24m 8s
i386-unknown	49s
nordic(yml)	9m 54s
	1h 56m 56s

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