[WIP] Ergonomic attribute macro for testing

[jackdfraser]

This PR is an attempt to introduce an attribute macro for testing with fantoccini as a dev dependency.

Essentially:

#[fantoccini::test(chrome, firefox)]
async fn end_to_end_test(client: Client) -> Result<(), CmdError>{

}

Upon being run the test will duplicate the test logic and run it against both chromedriver and geckodriver.

Ideally generating:

running 2 tests
test end_to_end_test::chrome ... ok
test end_to_end_test::firefox ... ok

Requirements:

• To make use of this macro in your cargo.toml requires having tokio, serial_test and fantoccini as dev-dependencies.

Notes:

• I added an example yew hello world program crate to demo the functionality.
• I borrowed from the existing (but currently private) tester! macro.

Areas Of Review Requested:

• I ignored the rustls feature and used Clientbuilder::native(). Why would someone use one vs the other?
• I removed the session_id Arc<Mutex> it wasn't clear to me that the code was making use of the session_id although perhaps that has something to do with my inexperience coding threads.

Future Features:

• Allow something like "chrome:9515" and "firefox:4444" and parse out the port numbers.

[jonhoo]

I guess I'm not quite clear on how much value this really provides — it's not as though there's lots of boilerplate to setting up the tests, and it's pretty easy to do it through a regular function (see our own test suite). If anything, I think I'd want this to live in a separate crate in its own repo. I don't think it's something that needs to live in fantoccini itself.

[codecov[bot]]

Codecov Report

Merging #212 (eb4d2fe) into main (377e40b) will decrease coverage by 1.14%. The diff coverage is 0.00%.

Additional details and impacted files

| [Impacted Files](https://codecov.io/gh/jonhoo/fantoccini/pull/212?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jon+Gjengset) | Coverage Δ | | |---|---|---| | [src/common.rs](https://codecov.io/gh/jonhoo/fantoccini/pull/212?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jon+Gjengset#diff-c3JjL2NvbW1vbi5ycw==) | `0.00% <0.00%> (ø)` | | | [src/lib.rs](https://codecov.io/gh/jonhoo/fantoccini/pull/212?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Jon+Gjengset#diff-c3JjL2xpYi5ycw==) | `93.10% <ø> (ø)` | |