Add Signale logger

[JasonEtco]

Why?

This PR adds Signale, a really nice logging utility that comes with a great looking output in the Actions UI. Here's a screenshot:

Code	Screenshot

This is accessible as tools.log:

tools.log('Log a thing!')
tools.log.info('Log something else!')

Closes #5

How?

I've basically just exported an instance of Signale, with the underlineLabel option disabled - in my testing, this was the difference between the above nice image and a huge whitespace area. The underline wouldn't render anyway, so it was causing issues 🤷‍♂️

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• Tests have been added/updated (if necessary)
• Documentation has been updated (if necessary)

[JasonEtco]

Worked on some docs, here it is rendered:

This is totally shippable right now, but I'd love to try to get tools.log() to work as a method (technically a callable class) - it'd basically work like:

const logger = new Signale()
tools.log = logger.info
Object.assign(tools.log, logger)

I'm certain that TypeScript will give me heck for that though. Added in b6f05bc!