Documentation to adapt to different target

[simojo]

First of all, this is a great contribution and really appreciate your work here.

I am curious if we could add documentation that details how to change the project's target from the one you gave as an example.

[martincvitic19]

I agree, this would be super useful!

[prtzl]

Glad to see people finding this repo useful. I'll check if I have another board lying around with at least different core and set of peripherals so that the necessary changes may be visible.

Moving within STM32 should be fairly easy changing just the cortex settings and linker script names and include path names.

Going to another device (brand) should only require similar amount of work. I'll see if I have some stuff around for this.

[martincvitic19]

I went through a tedious process of converting this repo to be able to build for STM32H743IT. I managed to pull it off and it works well but I think it would be useful to add another section in the README.md on how to switch targets (i.e. which files should one modify to simply start working with another target).

P.S. Thank once again for this repo, it greatly reduces the pain of working with STM32 boards