Improve quick start docs

[TheZoq2]

I recently helped a friend start using this and noticed some documentation problems which this hopefully fixes:

• Programs to install wasn't documented
• Having to specify target when compiling
• linker, gdb and cargo config wasn't documented
• inline example was out of date (replaced with a link to the example)

I also decided to remove some redundant text from lib.rs and link to README instead, just to avoid having some parts of the docs drift out of date.

Oh, and I fixed the docs.rs build, so this closes #154

The docs are very linux centric at the moment, but I have no idea what the process is like on windows.

cc @FredTheDino who ran into all these issues :)

[therealprof]

This looks like a rebranded Chinesium ST-Link clone with pirated firmware (not sure how they can offer that on in the adafruit line). Can we recommend a genuine product instead (like the ST-Link V3 Mini) which is even cheaper, though quite a bit trickier to obtain, insteads?

[therealprof]

Alternatively we could recommend an open product or maybe hint to an official Nucleo board which happens to include an ST-Link so works out-of-the-box.

[TheZoq2]

I think we should use something compatible with blue pills since they seem pretty common in the rust community.

Recommending a better alternative to the weird stlink sounds like a good idea, got a link to one?

[therealprof]

Any debug probe should be compatible with the blue pill. The question is only whether we want to stay with a native ST solution or recommend something else. The ST-Link v3 mini can be found here: https://www.st.com/en/development-tools/stlink-v3mini.html

[therealprof]

Maybe also include a few words about putting that into a .cargo/config here? Can also do this as a follow up.

[therealprof]

Uhm, that really should go in the section above as it is required (or at least useful in case of the .cargo/config) to build the software.

[TheZoq2]

Yea, that might be a good idea.

However, my point in ordering it like this is that the project successfully compiles after the cargo build line. If people get there and build fails, they have less things to check when debugging.

[therealprof]

If you don't have a memory.x there's a good chance it will not compile or throw linker errors (depending on circumstances) so that should go before any attempts to compile it. .cargo/config is a wash but would simplify the change for error in the naked cargo build above.

[TheZoq2]

I upgraded the text according to your comments

[therealprof]

Wrong link

[TheZoq2]

Oops, fixed

[therealprof]

Suggested change

	Create a new rust project as you usually do with `cargo init`. The hello world
	Create a new Rust project as you usually do with `cargo init`. The hello world

[therealprof]

Suggested change

	the background
	the background.

[TheZoq2]

I fixed the remaining issues and reworded the gdb section which sounded a bit strange after the updates. Mind giving it another look? @therealprof

[burrbull]

features = ["rt", "stm32f103", "medium"]

[therealprof]

LGTM