check whether username exist in proton or not

check_proton_mail_exit.js

await fetch("https://account.proton.me/api/users/available?Name=0xdeepmehta%40protonmail.com&ParseDomain=1", {
  "headers": {
    "accept": "application/vnd.protonmail.v1+json",
    "accept-language": "en-GB,en;q=0.6",
    "cache-control": "no-cache",
    "pragma": "no-cache",
    "sec-fetch-dest": "empty",
    "sec-fetch-mode": "cors",
    "sec-fetch-site": "same-origin",
    "sec-gpc": "1",
    "x-pm-appversion": "web-account@5.0.6.3",
    "x-pm-locale": "en_US"
  },
  "referrer": "https://account.proton.me/signup?plan=free&billing=12&currency=EUR&language=en",
  "referrerPolicy": "strict-origin-when-cross-origin",
  "body": null,
  "method": "GET",
  "mode": "cors",
  "credentials": "include"
});