Docs: InitialiSation or initialiZation

### Describe the problem

Both are used currently:
https://github.com/search?q=repo%3Asveltejs%2Fsvelte%20initialization&type=code

https://github.com/search?q=repo%3Asveltejs%2Fsvelte%20initialisation&type=code

But initialisation is used more often. I guess because of Rich :)

### Describe the proposed solution

Can we stick with one or the other?

### Importance

nice to have