non_ascii_literal example should be more verbose

Currently, the doc for non_ascii_literal isn't showing what to do better.

I think including a "Could be written:" example would be helpful. Just like clippy does in the console.

Instead of just let x = "Hä?".
Something like this would be better.

 String::from("€");
    |         ^^^
    |
    = help: Consider replacing the string with:
            ""\u{20ac}""

I can make a PR, if someone tells me where I can find this lint :)

[flip1995]

You can find the documentation of this lint here:

rust-clippy/clippy_lints/src/unicode.rs

Lines 35 to 38 in 58e1213

	/// **Example:**
	/// ```rust
	/// let x = "Hä?"
	/// ```

---

If you want to do some extra work, to make the lint even better, you can change these span_help_and_lint:

rust-clippy/clippy_lints/src/unicode.rs

Lines 102 to 115 in 58e1213

	span_help_and_lint(
	cx,
	NON_ASCII_LITERAL,
	span,
	"literal non-ASCII character detected",
	&format!(
	"Consider replacing the string with:\n\"{}\"",
	if is_allowed(cx, UNICODE_NOT_NFC, id) {
	escape(string.chars())
	} else {
	escape(string.nfc())
	}
	),
	);

with span_lint_and_sugg, so that the suggestion is displayed more idiomatically and is auto-fixable.

The applicability should me MachineApplicable.