update `collect` help

[hrenaud]

Run Lighthouse and save the results to a local folder.

Options:
      --help            Show help                                      [boolean]
      --version         Show version number                            [boolean]
  -d, --demo            Use demo File.                [boolean] [default: false]
  -u, --url             URL to process, supports multiple values         [array]
  -j, --json-file       Structured file, must respect a schema (see documentatio
                        n).                                             [string]
  -h, --extra-header    Extra object config for Lighthouse. JSON string or path
                        to a JSON file.                 [string] [default: null]
  -p, --output-path     Output folder.           [string] [default: "./reports"]
  -o, --output          Reporter for the results, supports multiple values. choi
                        ces: "json", "html", "statement". WARN: "csv" is not ava
                        lailable.                   [string] [default: ["html"]]
  -a, --audit-category  Audit to run, supports multiple values.
  [array] [default: ["performance","seo","accessibility","best-practices","light
                                                        house-plugin-ecoindex"]]

• [x] -d, --demo Use demo File. -> Use demo internal datas.
• [ ] -o, --output -> default is not only HTML !
• [x] -p, --output-path Output folder. [string] [default: "./reports"] -> .reports/<date-time>