Add When to use it / When not to use it sections

[wooorm]

Subject of the feature

A section in the readme and on the website that lists where using alex does and doesn’t make sense

Problem

As this is lacking, folks stumbling on alex assume that it does wildly different things.

Expected behaviour

It should be clarified that alex was made for technical docs, theses, etc.: text that shouldn’t assume context. Not for fiction or when texting your partner or so.

Alternatives

n/a