feat: move /organisations to /organizations

[10xLaCroixDrinker]

Description

This PR moves the /organisations route to /organizations and adds a redirect from the old route to the new.

Related Issues

Related to discussion in fastify/fastify#5349

Check List

• [x] I have read the Contributing Guidelines

[10xLaCroixDrinker]

Do you mean a server side redirect?

There's a client side redirect added in the docusaurus config at lines 208-213

[jsumners]

lgtm

Can we add a redirect somehow? cc @jsumners

Yes, we can add a page rule in Cloudflare for this (though it will use up one of our three available).

[Eomm]

We handle redirects here:

https://github.com/fastify/website/blob/37c6deaccf70e3ddfa1bca1e6a76db78e8ea05f9/docusaurus.config.utils.js#L75

but: https://prowritingaid.com/organisation-vs-organization

and the previous website stands with organisations: https://github.com/fastify/website-metalsmith/blob/master/src/website/content/organisations.md

[Eomm]

Could you update the PR? we fixed the deploy to staging.

Plus: why we don't add a redirect from organizations to organisations instead? this would ease the job

[gurgunday]

It was because the website uses American English everywhere else