Make sure PR from Forks don't get included in PR preview and don't trigger build/deployment workflow

[atteggiani]

Overview

PR from forks currently shouldn't be included in the PR previews.
However, a PR from a fork, would still trigger the build/deployment of the website (once the workflow run has been accepted), but this shouldn't happen.

Close Criteria

Make sure PR from forks don't trigger the build/deployment workflow.

[paigem]

Thanks @atteggiani - can you remind me why it's important that we don't have a PR preview for a PR made from a fork?

[atteggiani]

Main reason is safety.
We cannot know in advance that PRs from forks (that could come from anyone) don't contain malicious code that, when executed within a PR preview, might generate issues.

[paigem]

Got it, thanks! That's a very good reason. 😊