doc: Comparison to Ecosystem (including Rust std impl) [doc: 4/N]

[phip1611]

This is split-out 4/N from #1264 to improve reviewability.

This:

• adds a minimal example in lib.rs so that readers know what to expect from the crate
• compares uefi to other impls in the ecosystem, especially to the std impl for Rust
• adds a minimal example for a Rust app built with std and uefi

Steps to Un-draft

• merge doc: add comprehensive About section to lib.rs [doc: 3/N] #1291 and rebase onto

Checklist

• Sensible git history (for example, squash "typo" or "fix" commits). See the Rewriting History guide for help.
• Update the changelog (if necessary)

[nicholasbishop]

The MSRV section was already added to lib.rs in a previous PR, so this can be dropped.

[phip1611]

Sorry, artifact from a big rebase - I missed that.

[nicholasbishop]

The duplicate MSRV section is still present

[phip1611]

What?! How? I definitely removed that locally.

Sorry.. I really have no clue how this happened.

[phip1611]

Nice! I will split the "rust-std-example" into a dedicated MR. Can you approve it in its current state, please?

[nicholasbishop]

With ignore there's a good chance the code will stop compiling over time (in fact currently it's missing a use uefi::println). It's tricky to get no_std code compiling in a doc test, so how about linking to a file that is already tested by CI? Example:

//! ```ignore
#![doc = include_str!("../../template/src/main.rs")]
//! ```

[phip1611]

Oh, great idea! Thanks

[phip1611]

I'm very happy about the recent documentation additions, especially this one and #1331. This helps, I hope, to position ourself in the long term as the ones that define what is relevant, convenient and practical in UEFI with Rust and how the APIs should be designed, as std and the ecosystem grow closer together