Consider moving GSOC content into a single top-level folder

[dempseyatgithub]

There are currently 6 different GSOC directories at the top level of the repository, with the prospect of one being added every year.

Each of these top-level items are for a single page.

It would probably make sense to move to a structure where there is a single gsoc directory with a separate directory per year:

gsoc2019 -> gsoc/2019
gsoc2020 -> gsoc/2020
gsoc2021 -> gsoc/2021
gsoc2022 -> gsoc/2022
gsoc2023 -> gsoc/2023
gsoc2024 -> gsoc/2024

There would need to be a permanent redirect added, so existing links continue working.

[dempseyatgithub]

It may make sense to do this sort of consolidation into directories in a number of areas.

For example:

• Migration guides: There will soon be another one for Swift 6 soon. Moving to a migration-guide directory may make sense.

• Workgroups: When the site started there were a couple of workgroups. There are now six. A workgroup directory may make sense.

[dempseyatgithub]

If this were to be done, it would make sense to do them at one time so permanent redirects could be added at one time.

[dempseyatgithub]

@federicobucchi I noticed you assigned yourself the issue.

I added the 'workgroup to discuss' tag because I think this warrants a discussion in the workgroup and a plan for exactly what changes are intended (redirects, etc.) before implementing it.

[ktoso]

I'd be okey with that (I handle our GSoC participation in recent years) but please keep the old links working, they are "source of truth" for our gsoc applications and we really should not break the old links as https://summerofcode.withgoogle.com/programs/2024/organizations/swift links to them

It seems only the latest ideas page is linked to though AFAICS and this we can change 🤔 But still, many links on forums and swift blog link to these, so I'd request keeping the links functional 🙏