Add functions rust

[uchitsa]

for issue #9

[yegor256]

@uchitsa thanks for the contribution! The code looks good, but some CI workflows don't pass. Please, check.

[uchitsa]

@yegor256 let's try the workflows again please

[uchitsa]

Run aws-actions/configure-aws-credentials@v4
Error: Credentials could not be loaded, please check your action inputs: Could not load credentials from any providers

@yegor256 what should I do for fix it?

[yegor256]

@uchitsa try to push to the branch one more time, you should see the output of a new CI job I just added, it will help

[uchitsa]

@yegor256 FYI PR returns 404 for me. I try to push to the branch.

[yegor256]

@uchitsa the CI is still broken, see the output of the local job

[kreinba]

Requesting changes on one correctness defect at rust/functions.rs:39. The new fibo returns 1 for x<2, which shifts the sequence by one position relative to cpp/functions.cpp and rust/recursion.rs, both of which return x so fib(0)=0. The whole repo compares implementations of the same algorithm across languages, so this file needs to produce the same numbers. The matrix file mirrors the cpp version correctly. Inline comment below.