Custom path to save a panic report

Currently Report::persist uses env::temp_dir() to get a base folder to save a panic report

    /// Write a file to disk.
    pub fn persist(&self) -> Result<PathBuf, Box<dyn Error + 'static>> {
        let uuid = Uuid::new_v4().hyphenated().to_string();
        let tmp_dir = env::temp_dir();
        let file_name = format!("report-{}.toml", &uuid);
        let file_path = Path::new(&tmp_dir).join(file_name);
        let toml = self.serialize().expect("only using toml-compatible types");
        std::fs::write(&file_path, toml.as_bytes())?;
        Ok(file_path)
    }

However on some platforms TMPDIR may not be defined or be RO (yes, weird but true) . Sure TMPDIR may be overwritten when starting application however it would be nice to configure a base dir either as a parameter to ::handle_dump (breaking change) of through Metadata object

Start by reading Report::persist and the ::handle_dump and Metadata entry points mentioned in the issue to understand where the report directory is selected. Decide how the base directory should be configured, then verify that a report can be written to the configured location while preserving the existing default behavior.