fix: updated the download URL

[anshukrs]

-Updated the download URL from https://terasology.org/download to https://terasology.org/downloads/

Fixes #690

[jdrueckert]

Thanks for the contribution @anshukrs!
Approved, but we'll need to fix the push validation action first, before merging it. I'll have a quick look now, but if it's nothing trivial, it will need to wait until tomorrow.

PS: I added "Fixes <issue-nr>" which will instruct GitHub to auto-close the referenced issue once the PR gets merged. Also, I adjusted the PR title to match our guidelines.

[jdrueckert]

Interestingly, for other PRs the Test Report Upload works (see here for example), but on yours it doesn't... Guess I'll need to dig some more tomorrow or on the weekend.

[jdrueckert]

Seems like the GitHub Action has some issues with PRs coming from forks 🙄
We'll need to either debug and fix the action or divert to using another one. I'll create an issue for that.

Until we get to that, I believe it's fine to merge this PR without the action succeeding - after all it's a minor change that doesn't touch any of the launcher's logic, etc. So thank you for the contribution @anshukrs and congratulations to your first launcher PR being merged 👏