Add [example] tags to cargo.toml

[JoelCodes]

I'm a bit new to Rust, but it would be easier to run the examples if they were added to the cargo.toml file (as desscribed here).

[mitchmindtree]

Thanks for the issue @JoelCodes!

Would you mind sharing why you would find it easier to run examples this way?

Normally I only see examples listed explicitly in a package's Cargo.toml when the example requires a certain feature, or has some non-standard directory structure (e.g. not a single file under examples/). By listing the example and its features explicitly within the Cargo.toml, the user no longer has to manually specify necessary features when running the example, e.g. rather than cargo run --features "foo bar" --example baz, the user can just run cargo run --example baz.

In our case however, our examples do not require any specific features to run, so there is no extra benefit in this sense. Please let me know if I'm missing something!