Reorganize the website structure

[ebetica]

This PR reorganizes the website structure, so we now have:

en/
  index.md
  about.dm
  week01/
  week02/
  ...
zh/
  index.md
  about.md
  week01/
  week02/
  ...
...

Hopefully it's less messy and easier to work with.

After this is merged, I will pull the images out into a global directory as well.

Also fixes some broken links in zh/index.md

[ebetica]

This is a hack since the default language has a special index.md. We symlink it and exclude en/index.md.

[Atcold]

I believe there are many many broken links now, pointing to the original chapters which now has to become weekXX.

[ebetica]

Fixed all of them, grep -r 'en/0' and grep -r 'zh/0' gives nothing now.

[Atcold]

Can you plz rebase on top of master? There have been updates to 01-1.md and 01-2.md.

[ebetica]

Yes, it has been rebased.

[Atcold]

I don't think you've rebased.

[ebetica]

I rebased again - I found the problem, the .gitignore was ignoring all the image files, so I enabled it for the docs/ dir.

[Atcold]

Okay, how about we coordinate on Messenger your rebase with my merging?
Here I cannot get this to join master.
Or just drop by my office?

[ebetica]

I could just hit the merge button, if you trust I won't introduce any new bugs in the rebase? Otherwise if this happens again (I can ping you|you can ping me) on messenger about it. As long as no other PRs are merged I think the button will stay green:

Everybody with an open PR will unfortunately have to rebase.

[Atcold]

Let's get the images out now! 😬