Add ability to change the size of the logo on the login screen.

[OwainJ]

The size of the logo on the login screen is tailored to the size of the Umbraco logo, so when we customise the Login screen to include a client logo, the sizing can look way off. Therefore, the ability to adjust the size of the logo would be incredibly useful to ensure that client logos look good on the login screen.

[iOvergaard]

This makes sense to me. I believe we set both width and height properties on the logo, which naturally only allows for a specific ratio. We should make it configurable or, as a compromise, only set the height attribute.

[nul800sebastiaan]

Looks like it's already only height

[OwainJ]

If we could configure the logo height using a CSS variable, in the same way we can configure other aspects of the login screen, that would be great!

(https://docs.umbraco.com/umbraco-cms/13.latest/fundamentals/backoffice/##custom-css)

[OwainJ]

E.g. if a client has a particularly square or tall logo, then it will currently look quite small compared to a wider logo like the Umbraco logo.

[iOvergaard]

@OwainJ I created #18499 to try and make up for this. It should use the same variables on both the login screen and the backoffice.

[iOvergaard]

This should hopefully be resolved with #18499, which is due for release in 15.4.0. I have matched up the CSS variables across the login screen and backoffice, so you should be able to adjust any custom logos through a single CSS file, if you load it up through a public extension by setting "public": true in the umbraco-package.json file.

[OwainJ]

That's awesome!! Thank you!