2.12.0: Reduced filter boilerplate

• Changed filters API so that any web.Filter implementation can use
  yield from $invocation->proceed(...) without having to test whether
  handlers return a generator first, e.g. via is_iterable(). Filters
  using return $invocation->proceed(...) continue to work. Keep in mind
  they return before asynchronous handlers have completely executed!
  (@thekid)

2.11.0: Early hints, BC fix

• Merged PR #80: Fixed usage of "&" chars in multipart parameters
  (@johannes85)
• Fixed compatibility with older versions of xp-framework/networking
  without asynchronous server support. This lead to the server being
  started but not answering any request, see issue #79.
  (@thekid)
• Added support for HTTP status code 103 "Early Hints", see RFC 8297 and
  https://evertpot.com/http/103-early-hints. Note that this does not work
  in the development webserver, see php/php-src#7025.
  (@thekid)

2.10.0: HTTP dates

• Merged PR #77: Add Headers::date(int|util.Date) to return dates in GMT
  according to HTTP spec
  (@thekid)

2.9.1: Development server fix

• Fixed issue #75: Development server: Response already flushed - @thekid

2.9.0: FilesFrom headers

• Merged PR #74: Add new FilesFrom::with($headers) to add custom headers
  (@thekid)

2.8.0: Async

• Merged PR #73: Add new async method Response::transmit() replacing
  Response::transfer(). While existing code will continue to work, it
  should be rewritten as seen in the pull request!
  (@thekid)
• Merged PR #72: Asynchronous file handling for web.handler.FilesFrom.
  (@thekid)
• Added support for interruptible handlers. These handlers can hand back
  control to the server and allow for further requests to be handled by
  using yield. Typical usecases would be file uploads and downloads,
  during which the server would normally be blocked. See issue #70.
  (@thekid)

2.7.0: X-Content-Type-Options: nosniff

• Set Server header to XP to be able to distinguish responses
  (@thekid)
• Removed Host header, it's a request-only header. See
  https://webhint.io/docs/user-guide/hints/hint-no-disallowed-headers/
  (@thekid)
• Added X-Content-Type-Options: nosniff to headers when serving static
  content via web.handlers.FilesFrom to prevent UAs from guessing. See
  https://webhint.io/docs/user-guide/hints/hint-x-content-type-options/
  (@thekid)

2.6.1: EOF fixes

• Fixed server being unresponsive after a file upload was cancelled
  during its transmission
  (@thekid)

2.6.0: Environment::path()

• Merged PR #68: Add Environment::path() utility method - @thekid

2.5.1: PHP 8.1 NULL fixes

• Fixed issue #69: Warnings with PHP 8.1 - @thekid