input validation errors

### Description of issue
Missing max character in the shop name input, license number input in sign up page.

```
Path: /pages/customer/addcustomer.html
Browser: Chrome 112.0.0.0 on Windows 10
Viewport: 1504 x 892 @1.5x
Language: en-GB
Cookies: Enabled
```

[Open in BrowserStack](https://www.browserstack.com/user/try-live?url=https%3A%2F%2Fdeploy-preview-1--mam-billing.netlify.app%2Fpages%2Fcustomer%2Faddcustomer.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--mam-billing.netlify.app/pages/customer/addcustomer.html)

Open pages/customer/addcustomer.html and locate the shop name and license number inputs in the sign-up form. Check the existing validation behavior, then define and add the missing maximum-length constraints; done means both fields reject values beyond their intended limits in Chrome.

Written by the indexing model from the issue text.