Disable the Web::Screenshot#process spec when running under GitHub Actions

[postmodern]

Apparently sometimes the Web::Screenshot#process spec sometimes fails, likely due to memory constraints.

Ferrum::ProcessTimeoutError:
  Browser did not produce websocket url within 10 seconds, try to increase `:process_timeout`. See https://github.com/rubycdp/ferrum#customization
  ./vendor/bundle/ruby/3.2.0/gems/ferrum-0.15/lib/ferrum/browser/process.rb:172:in `parse_ws_url'
  ./vendor/bundle/ruby/3.2.0/gems/ferrum-0.15/lib/ferrum/browser/process.rb:106:in `start'
  ./vendor/bundle/ruby/3.2.0/gems/ferrum-0.15/lib/ferrum/browser.rb:247:in `start'
  ./vendor/bundle/ruby/3.2.0/gems/ferrum-0.15/lib/ferrum/browser.rb:132:in `initialize'
  ./vendor/bundle/ruby/3.2.0/gems/ronin-web-browser-0.1.0/lib/ronin/web/browser/agent.rb:85:in `initialize'
  ./vendor/bundle/ruby/3.2.0/gems/ronin-web-browser-0.1.0/lib/ronin/web/browser.rb:127:in `new'
  ./vendor/bundle/ruby/3.2.0/gems/ronin-web-browser-0.1.0/lib/ronin/web/browser.rb:127:in `new'
  ./lib/ronin/recon/builtin/web/screenshot.rb:71:in `initialize'
  ./spec/builtin/web/screenshot_spec.rb:9:in `new'
  ./spec/builtin/web/screenshot_spec.rb:9:in `block (2 levels) in <top (required)>'
  ./spec/builtin/web/screenshot_spec.rb:25:in `block (3 levels) in <top (required)>'
  ./vendor/bundle/ruby/3.2.0/gems/webmock-3.23.1/lib/webmock/rspec.rb:39:in `block (2 levels) in <top (required)>'

We should check if the specs are currently running under GitHub Actions by checking for an ENV variable (GITHUB_TOKEN?) and call skip "<message here>".

    it "must visit a website and take a screenshot of it" do
      skip "GitHub Actions causes the Ferrum process to timeout sometimes" if ENV['GITHUB_TOKEN']
      ...
    end