Form validation

### Description of issue
Login ID and password fields don't have any validation.

### Expected result

### Actual result

### Steps to reproduce
1.
2.
3.

```
Path: /admin/admin%20html/admin/admin_main.html
Browser: Chrome 112.0.0.0 on Windows 10
Viewport: 1504 x 892 @1.5x
Language: en-US
Cookies: Enabled
```

[Open in BrowserStack](https://www.browserstack.com/user/try-live?url=https%3A%2F%2Fdeploy-preview-1--global-fun-city.netlify.app%2Fadmin%2Fadmin%2520html%2Fadmin%2Fadmin_main.html&os=Windows&os_version=10&browser=Chrome&browser_version=112.0&resolution=1504x892&speed=1&start=true&ref=netlify-source)

Submitted from [Netlify Deploy Preview #1](https://deploy-preview-1--global-fun-city.netlify.app/admin/admin%20html/admin/admin_main.html)

Open /admin/admin html/admin/admin_main.html and inspect the login ID and password fields. The issue provides no reproduction steps, expected behavior, or named tests, so first determine the intended validation rules from the surrounding admin page and project conventions. Done means both fields have the agreed validation behavior and the login flow still works in Chrome.

Written by the indexing model from the issue text.