shfmt - support simplifying (`-s`) and minifying flags (`-mn`)

`shfmt` supports [simplifying and/or minifying shell scripts](https://github.com/mvdan/sh/blob/master/cmd/shfmt/shfmt.1.scd#generic-flags). However, there is no support provided via `.editorconfig` for the flags. So we'll need some additional configuration in the shfmt Gradle DSL to enable these.

My thoughts are something akin to one of the following:

Option 1
```gradle
// Provides future extensible flexibility and follows the lead set by the `ktfmt` configuration
spotless {
shell {
shfmt().configure {
it.minify = true
it.simplify = true
}
}
}
```

Option 2
```gradle
// If any other options become available in the future, this seems to be less extensible, however, it is very readable
spotless {
shell {
shfmt()
.minify()
.simplify()
}
}
```

Note that minifying the code implies simplifying the code. So both flags can probably be true, but both flags aren't required to simplify and minify.

Parti dal punto di ingresso esistente della DSL Gradle di shfmt e analizza come vengono esposte altrove le opzioni del formatter, in particolare il pattern di configurazione di ktfmt menzionato nell’issue. Decidi tra proprietà configurabili e metodi fluent, quindi verifica che simplify e minify possano essere abilitati indipendentemente, mentre minify implica simplify.

Scritto dal modello di indicizzazione a partire dal testo della issue.