- Point at opening mismatched formatting brace
- Account for differences between raw and regular strings
- Account for differences between the code snippet and `InternedString`
- Add more tests
When encountering format string errors in a raw string, or regular
string literal with embedded newlines, account for the positional
change to use correct spans.
:drive by fix: 🚗
On cases of malformed format strings where a `{` hasn't been properly
escaped, like `println!("{");`, present a note explaining how to escape
the `{` char.
