Use webrick's escape instead of encode_www_form_component

```
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>
```

.gitlab-ci.yml

@@ -33,6 +33,10 @@ test:2.7:
   extends: .tests
   image: 'ruby:2.7'
 
+test:3.0:
+  extends: .tests
+  image: 'ruby:3.0'
+
 test:jruby:
   extends: .tests
   image: 'jruby:9.2.12-jre'

lib/validate_website/crawl.rb

@@ -46,7 +46,7 @@ def extract_imgs_from_page(page)
 
       page.doc.search('//img[@src]').reduce(Set[]) do |result, elem|
         u = elem.attributes['src'].content
-        result << page.to_absolute(URI.parse(URI.encode_www_form_component(u)))
+        result << page.to_absolute(URI.parse(WEBrick::HTTPUtils.escape(u)))
       end
     end
 

lib/validate_website/static_link.rb

@@ -8,7 +8,7 @@
 # rubocop:disable Metrics/BlockLength
 StaticLink = Struct.new(:link, :site) do
   def link_uri
-    @link_uri = URI.parse(URI.encode_www_form_component(link))
+    @link_uri = URI.parse(WEBrick::HTTPUtils.escape(link))
     @link_uri = URI.join(site, @link_uri) if @link_uri.host.nil?
     @link_uri
   end