Add BF config to INAV target converter

docs/development/Converting Betaflight Targets.md

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+If your flight controller does not have an official INAV target, it is possible to use src/utils/bf2inav.py script to generate a good starting point for an unofficial INAV target.
+
+This script can read the config.h from [Betaflight's target configuration repository](https://github.com/betaflight/config) and it currently supports STM32F405, STM32F722, STM32F745, STM32H743 and AT32F435 targets.
+Locate your Flight Controller target config.h in BetaFlight's repo, eg.: [config.h](https://github.com/betaflight/config/blob/master/configs/BETAFPVF405/config.h), for BETAFPVF435 target.
+
+It is also advisable to record the output of the timer command from BetaFlight, as it will provide useful information on `timer` usage that can be used to adjust the generated target later.
+
+```
+# timer
+timer B08 AF3
+# pin B08: TIM10 CH1 (AF3)
+timer C08 AF3
+# pin C08: TIM8 CH3 (AF3)
+timer B00 AF2
+# pin B00: TIM3 CH3 (AF2)
+timer B01 AF2
+# pin B01: TIM3 CH4 (AF2)
+timer A03 AF1
+# pin A03: TIM2 CH4 (AF1)
+timer A02 AF1
+# pin A02: TIM2 CH3 (AF1)
+timer B06 AF2
+# pin B06: TIM4 CH1 (AF2)
+timer A08 AF1
+# pin A08: TIM1 CH1 (AF1)
+timer A09 AF1
+# pin A09: TIM1 CH2 (AF1)
+timer A10 AF1
+# pin A10: TIM1 CH3 (AF1)
+```
+In the above example, `pin B08: TIM10 CH1 (AF3)` means that pind to CH1. This information can be used to fix the generated timer assigned to match BetaFlight's allocation by editing the `target.c` file generated by the `bf2inav.py` script.
+
+
+Using the BETAFPVF405 target mentioned above, to create the target now we need to:
+
+1. Download INAV source code and be able to build
+2. Download the config.h from BetaFlight repository
+3. Create a target folder that will be used as the output folder for the `bf2inav.py` script, eg: `inav/src/main/targets/BETAFPVF405`
+4. Navigate to the script folder in `inav/src/utils/`
+5. `python3 ./bf2inav.py -i config.h -o ../main/target/BETAFPVF405/`
+6. Edit generated `target.c` and  chose the correct timer definitions to match Betaflight's timer definitions.
+```
+timerHardware_t timerHardware[] = {
+    DEF_TIM(TIM3, CH3, PB0, TIM_USE_OUTPUT_AUTO, 0, 0),
+    //DEF_TIM(TIM8, CH2N, PB0, TIM_USE_OUTPUT_AUTO, 0, 0),
+    //DEF_TIM(TIM1, CH2N, PB0, TIM_USE_OUTPUT_AUTO, 0, 0),
+
+    DEF_TIM(TIM3, CH4, PB1, TIM_USE_OUTPUT_AUTO, 0, 0),
+    //DEF_TIM(TIM8, CH3N, PB1, TIM_USE_OUTPUT_AUTO, 0, 0),
+    //DEF_TIM(TIM1, CH3N, PB1, TIM_USE_OUTPUT_AUTO, 0, 0),
+
+    //DEF_TIM(TIM5, CH4, PA3, TIM_USE_OUTPUT_AUTO, 0, 0),
+    //DEF_TIM(TIM9, CH2, PA3, TIM_USE_OUTPUT_AUTO, 0, 0),
+    DEF_TIM(TIM2, CH4, PA3, TIM_USE_OUTPUT_AUTO, 0, 0),
+
+    //DEF_TIM(TIM5, CH3, PA2, TIM_USE_OUTPUT_AUTO, 0, 0),
+    //DEF_TIM(TIM9, CH1, PA2, TIM_USE_OUTPUT_AUTO, 0, 0),
+    DEF_TIM(TIM2, CH3, PA2, TIM_USE_OUTPUT_AUTO, 0, 0),
+
+    DEF_TIM(TIM8, CH3, PC8, TIM_USE_OUTPUT_AUTO, 0, 0),
+    //DEF_TIM(TIM3, CH3, PC8, TIM_USE_OUTPUT_AUTO, 0, 0),
+
+    DEF_TIM(TIM1, CH1, PA8, TIM_USE_OUTPUT_AUTO, 0, 0),
+
+    //DEF_TIM(TIM3, CH1, PB4, TIM_USE_BEEPER, 0, 0),
+
+    DEF_TIM(TIM4, CH1, PB6, TIM_USE_LED, 0, 0),
+
+};
+```
+In this particular example, PA3, PA2 were changed to match Betaflight's mapping, and the timer PB4 was disabled, due to a timer conflict. Normal channels are prefered over N channels (CH1, over CH1N) or C channels in AT32 architectures.
+7. Now update yout build scripts by running `cmake` and build the target you just created. The target name can be checked in the generated `CMakeLists.txt`, but should match the Betaflight target name.
+
+For information on how to build INAV, check the documents in the [docs/development](https://github.com/iNavFlight/inav/tree/master/docs/development) folder.