res.cookie option with sameSite 'none' throws TypeError: option sameSite is invalid at Object.serialize

### Related issues

I found the issue for Express framework
https://github.com/expressjs/express/issues/3958
and looks it was fixed there.

### [REQUIRED] Version info

node: v10.16.3

**firebase-tools:**

8.0.0.

### [REQUIRED] Test case

export const sameSiteCookie = functions.https.onRequest((req, res) => {
cors(req, res, () => {
const expiresIn = 60 * 60 * 24 * 5 * 1000;
const options: any = {
maxAge: expiresIn,
httpOnly: true,
secure: true,
sameSite: 'none',
};
res.cookie('testCKI', 'value123', options);
res.end(JSON.stringify({
data: {
status: 'success'
}
}));
});
});

### [REQUIRED] Steps to reproduce

calling the cloud function above

### [REQUIRED] Expected behavior

set cookie value to SameSite=Never

### [REQUIRED] Actual behavior

TypeError: option sameSite is invalid at Object.serialize (/worker/node_modules/cookie/index.js:174:15) at ServerResponse.res.cookie (/worker/node_modules/express/lib/response.js:853:36) at cors (/srv/lib/index.js:106:13) at cors (/srv/node_modules/cors/lib/index.js:188:7) at /srv/node_modules/cors/lib/index.js:224:17 at originCallback (/srv/node_modules/cors/lib/index.js:214:15) at /srv/node_modules/cors/lib/index.js:219:13 at optionsCallback (/srv/node_modules/cors/lib/index.js:199:9) at corsMiddleware (/srv/node_modules/cors/lib/index.js:204:7) at exports.sessionLogin.functions.https.onRequest (/srv/lib/index.js:98:5)

### Were you able to successfully deploy your functions?

no error messages seen

从提供的 TypeScript 测试用例以及 node_modules/cookie/index.js:174 和 express/lib/response.js:853 处的堆栈跟踪开始；将依赖项的行为与相关的 Express issue #3958 进行比较。使用 firebase-tools 8.0.0 重现，并确认 res.cookie 接受 sameSite: 'none'，且在没有 TypeError 的情况下发出预期的 cookie。

由索引模型根据 Issue 内容生成。