log_out.js: Fix for WebKit

My guess is that hidden forms are broken or forbidden on it.
This greatly simplifies the code anyway.

Tested in: WebKitGTK 2.28.3, Firefox 78.0.2-1, Chromium 84.0.4147.89-1
Closes: #85

app/javascript/flavours/glitch/util/backend_links.js

 export const preferencesLink = undefined; // '/settings/preferences';
 export const profileLink = undefined; // '/settings/profile';
-export const signOutLink = undefined; // '/auth/sign_out';
+export const signOutLink = '/auth/sign_out';
 export const termsLink = undefined; // '/terms';
 export const accountAdminLink = (id) => `/pleroma/admin/#/users/${id}/`;
 export const statusAdminLink = (account_id, status_id) => `/pleroma/admin/#/users/${account_id}/`;

app/javascript/flavours/glitch/util/log_out.js

@@ -2,33 +2,9 @@ import Rails from '@rails/ujs';
 import { signOutLink } from 'flavours/glitch/util/backend_links';
 
 export const logOut = () => {
-  const form = document.createElement('form');
-
-  const methodInput = document.createElement('input');
-  methodInput.setAttribute('name', '_method');
-  methodInput.setAttribute('value', 'delete');
-  methodInput.setAttribute('type', 'hidden');
-  form.appendChild(methodInput);
-
-  const csrfToken = Rails.csrfToken();
-  const csrfParam = Rails.csrfParam();
-
-  if (csrfParam && csrfToken) {
-    const csrfInput = document.createElement('input');
-    csrfInput.setAttribute('name', csrfParam);
-    csrfInput.setAttribute('value', csrfToken);
-    csrfInput.setAttribute('type', 'hidden');
-    form.appendChild(csrfInput);
-  }
-
-  const submitButton = document.createElement('input');
-  submitButton.setAttribute('type', 'submit');
-  form.appendChild(submitButton);
-
-  form.method = 'post';
-  form.action = signOutLink;
-  form.style.display = 'none';
-
-  document.body.appendChild(form);
-  submitButton.click();
+  fetch(signOutLink, {
+    method: 'DELETE'
+  }).then(() => {
+    window.location = '/web/';
+  });
 };