Modernise & move current (largely legacy) tutorials out of main pygame repository into their own repository

[MyreMylar]

The current tutorials are largely old, plus there are some translations that are not really organised. The main pygame code docs will never be translated because they change too frequently so a documentation language switcher there doesn't really work.

I think the tutorials could benefit from being pulled out entirely from the main code repository and it's documentation theming into their own thing which could have more modern support for translations (sphinx does support this).

Step 1: would just be to open a new repo with only the docs part of the tutorials in it and get them building again locally.

Step 2: would be a new proper index page of what was in the tutorials.

Step 3: would be organising the existing translations so toggling a language switcher took you to the proper translations.

Step 4: would be integrating it back into this website so the current 'tutorials' link took you to the built result of the tutorials repository rather than halfway down the docs front page. Also opening a PR to remove the (at this point duplicate) tutorials from the main pygame-ce code repository.

Step 5:* would ideally be a modernisation review/trimming of the existing text tutorials so that they were relevant and an opening up of the repository to accept PRs for things like video tutorials (if people wanted to submit them).