Update license from MIT to EUPL v. 1.2

[RoelvandenBerg]

Replaced MIT License with European Union Public Licence v. 1.2.

Description

What have you changed and why?

Type of change

(Remove irrelevant options)

• Minor change (typo, formatting, version bump)
• New feature
• Improvement of existing feature
• Bugfix
• Refactoring
• Configuration change
• Breaking change

Checklist:

• I've double-checked the code in this PR myself
• I've left the code better than before (boy scout rule)
• The code is readable, comments are added that explain hard or non-obvious parts.
• I've expanded/improved the (unit) tests, when applicable
• I've run (unit) tests that prove my solution works
• There's no sensitive information like credentials in my PR

[rkettelerij]

Oh graag de license ind e readme ook aanpassen: https://kadaster.atlassian.net/browse/PDOK-16148

[rkettelerij]

Even als https://github.com/PDOK/uptime-operator/blob/master/hack/boilerplate.go.txt

[rkettelerij]

zie comments