docs: Fix link to UCUM website

[liwa-datev]

Update the link to ucum to a working one and an examples site.

[linux-foundation-easycla]

• ❌ - login: @liwa-datev / name: Lion Wagner . The commit (62c8a67) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please submit a support request ticket.

[jmacd]

Thank you @liwa-datev

[jsuereth]

@liwa-datev You need to sign the CLA before we can merge this

[liwa-datev]

@liwa-datev You need to sign the CLA before we can merge this

Thank you for the reminder and the patience, I will have to set up the CLA with my employer which could take a couple of days.

[bogdandrutu]

@liwa-datev can you please sign the CLA?

[liwa-datev]

@liwa-datev can you please sign the CLA?

Unfortunately, I'm still waiting on the authorization to easy CLA from by employers CLA Manger.

[tigrannajaryan]

The old link seems to work fine for me. What's the problem with it?

[arminru]

I believe it used to be down but now it seems to be available again.
On https://github.com/ucum-org/ucum they link to https://ucum.org/ucum though, so this seems to be the preferred page that's more likely to be available long-term.