ch1: Support view-source scheme

[corona10]

In addition to HTTP and HTTPS, there are other schemes, such as view-source; navigating in a real browser to view-source:browser.engineering/http.html shows the HTML source of this chapter rather than its rendered output. Add support for the view-source scheme. Your browser should print the entire HTML file as if it was text. Hint: To do so, you can utilize the entities from the previous exercise, and add an extra transform() method that adjusts the input to show() when in view-source mode, like this: show(transform(body))

• Python
• Rust