feat: add/set no-color feature for testing

[zjp-CN]

fix https://github.com/josecelano/cargo-pretty-test/issues/13 and suppress https://github.com/josecelano/cargo-pretty-test/pull/14

With this PR, you can use any of these commands to run tests:

• cargo test --features no-color
• cargo test -F no-color
• cargo t
• cargo test --all-features (which CI does)

[josecelano]

Hi @zjp-CN, I was wondering if it wouldn't make more sense to set "no-color" as the default and "with-color" as the feature. For me, a negative feature looks weird.

For the cargo run --color option. The default option is auto.

Do you think we should do the same?

And you can also specify the value with a config value.

https://doc.rust-lang.org/cargo/reference/config.html

I have the impression that by default, we should not use color, because It would make testing easier. And then we can have unit tests for the colorized output. However, I have not had time to read the code and think about it carefully.

[josecelano]

ACK f5deb0965e73de5f6822a0fd7c02346c0a64fada