Cypress typescript (#13591)

* convert Cypress tests to TypeScript

this work was done by @lunaisnotaboy https://github.com/lunaisnotaboy
for their fork https://github.com/cutiekey/cutiekey/pull/7

I just repacked their changes into a minimal set

* fix call to `window` in cypress tests

this error was spotted thanks to the TypeScript compiler:

```
support/commands.ts:33:12 - error TS2559: Type '(win: any) => void'
has no properties in common with type 'Partial<Loggable &
Timeoutable>'.

33  cy.window(win => {
              ~~~~~~~~

Found 1 error in support/commands.ts:33
```

(again, @lunaisnotaboy did the actual work)

cypress/support/commands.ts

@@ -0,0 +1,60 @@
+// ***********************************************
+// This example commands.js shows you how to
+// create various custom commands and overwrite
+// existing commands.
+//
+// For more comprehensive examples of custom
+// commands please read more here:
+// https://on.cypress.io/custom-commands
+// ***********************************************
+//
+//
+// -- This is a parent command --
+// Cypress.Commands.add('login', (email, password) => { ... })
+//
+//
+// -- This is a child command --
+// Cypress.Commands.add('drag', { prevSubject: 'element'}, (subject, options) => { ... })
+//
+//
+// -- This is a dual command --
+// Cypress.Commands.add('dismiss', { prevSubject: 'optional'}, (subject, options) => { ... })
+//
+//
+// -- This will overwrite an existing command --
+// Cypress.Commands.overwrite('visit', (originalFn, url, options) => { ... })
+
+Cypress.Commands.add('visitHome', () => {
+	cy.visit('/');
+	cy.get('button', { timeout: 30000 }).should('be.visible');
+})
+
+Cypress.Commands.add('resetState', () => {
+	cy.window().then(win => {
+		win.indexedDB.deleteDatabase('keyval-store');
+	});
+	cy.request('POST', '/api/reset-db', {}).as('reset');
+	cy.get('@reset').its('status').should('equal', 204);
+	cy.reload(true);
+});
+
+Cypress.Commands.add('registerUser', (username, password, isAdmin = false) => {
+	const route = isAdmin ? '/api/admin/accounts/create' : '/api/signup';
+
+	cy.request('POST', route, {
+		username: username,
+		password: password,
+	}).its('body').as(username);
+});
+
+Cypress.Commands.add('login', (username, password) => {
+	cy.visitHome();
+
+	cy.intercept('POST', '/api/signin').as('signin');
+
+	cy.get('[data-cy-signin]').click();
+	cy.get('[data-cy-signin-username] input').type(username);
+	cy.get('[data-cy-signin-password] input').type(`${password}{enter}`);
+
+	cy.wait('@signin').as('signedIn');
+});