Add Example: HTTP server: Upload file to Deno by Example

[davis9001]

Created a TypeScript file in /examples to illustrate a very basic approach to using Deno.serve() to facilitate uploading files using HTML forms, along with a resource link to Fresh docs to do the same.

Note: I couldn't find any way around encoding the form HTML string to get it to show on the docs page: Lume or whatever isn't auto encoding in the <code> block. This also led me to find what I believe is another bug in Deno docs (or Lume? or codemirror?) not display the generic class (presumably because it's getting interpreted as an HTML element.)

Anyway to make sure the code actually works (and displays on the docs) I used @std/html/entities unescape() on the encoded HTML string before sending it off in the Response.

Closes #42

[davis9001]

Request for review @thisisjofrank

[davis9001]

Request for review @philhawksworth 🫡

[thisisjofrank]

Thanks for this example! I'll take a look at how the examples pages are being generated and see if I can fix that html encoding bug.