doc: add partitioned and priority for cookies (#1816)

sync latest cookie options

docs/api/context.md

@@ -84,6 +84,8 @@ Koa uses the [cookies](https://github.com/pillarjs/cookies) module where options
 * `domain`: a string indicating the domain of the cookie (no default).
 * `secure`: a boolean indicating whether the cookie is only to be sent over HTTPS (`false` by default for HTTP, `true` by default for HTTPS). [Read more about this option](https://github.com/pillarjs/cookies#secure-cookies).
 * `httpOnly`: a boolean indicating whether the cookie is only to be sent over HTTP(S), and not made available to client JavaScript (`true` by default).
+* `partitioned`: a boolean indicating whether to partition the cookie in Chrome for the [CHIPS Update](https://developers.google.com/privacy-sandbox/3pcd/chips) (`false` by default). If this is true, Cookies from embedded sites will be partitioned and only readable from the same top level site from which it was created.
+* `priority`: a string indicating the cookie priority. This can be set to `'low'`, `'medium'`, or `'high'`.
 * `sameSite`: a boolean or string indicating whether the cookie is a "same site" cookie (`false` by default). This can be set to `'strict'`, `'lax'`, `'none'`, or `true` (which maps to `'strict'`).
 * `signed`: a boolean indicating whether the cookie is to be signed (`false` by default). If this is true, another cookie of the same name with the `.sig` suffix appended will also be sent, with a 27-byte url-safe base64 SHA1 value representing the hash of _cookie-name_=_cookie-value_ against the first [Keygrip](https://www.npmjs.com/package/keygrip) key. This signature key is used to detect tampering the next time a cookie is received.
 * `overwrite`: a boolean indicating whether to overwrite previously set cookies of the same name (`false` by default). If this is true, all cookies set during the same request with the same name (regardless of path or domain) are filtered out of the Set-Cookie header when setting this cookie.