Some minor improvements

- bundle install with job
- pointing exact '3.0' not 3

Support ruby 3

```
irb(main):001:0> require 'webrick'
=> true
irb(main):002:0> URI.parse(URI.encode_www_form_component("http://example.com/path?query=あああ"))
=> #<URI::Generic http%3A%2F%2Fexample.com%2Fpath%3Fquery%3D%E3%81%82%E3%81%82%E3%81%82>
irb(main):003:0> URI.parse(WEBrick::HTTPUtils.escape("http://example.com/path?query=あああ"))
=> #<URI::HTTP http://example.com/path?query=%E3%81%82%E3%81%82%E3%81%82>
```

ref:
- uri encoding: https://docs.knapsackpro.com/2020/uri-escape-is-obsolete-percent-encoding-your-query-string
- agument splat: https://www.ruby-lang.org/en/news/2019/12/12/separation-of-positional-and-keyword-arguments-in-ruby-3-0/
- bundle webrick: https://www.ruby-lang.org/en/news/2020/12/25/ruby-3-0-0-released/

https://checker.html5.org/ gives a 502

https://www.ruby-lang.org/en/news/2018/06/20/support-of-ruby-2-2-has-ended/

ref https://github.com/htacg/tidy-html5/issues/65

Improve start message for static validator

ref https://github.com/spk/validate-website/issues/19