In dark mode, the Rust icon is almost unnoticeable

[leandronsp]

While using dark mode on Github, the Rust icon is unnoticeable, which gives the impression that the exercise is missing the Rust implementation.

Tried to use inline CSS in this PR, but it's not ideal since it wouldn't work well in other versions.

Ideally, we should overcome that by changing directly the SVG, maybe.

[IndranjanaChatterjee]

I would like to work on this issue to achieve the required changes using dark mode on Github . Please assign it to me.

[kelvins]

Fixed by #232