Enable pdf generation in prs; fix chapter structure

[lakesare]

In this PR:

• [x] Generate all .md files

  Explanation: In previous PR I thought .md files will be automatically generated on push to master, they weren't, so pushing the final .md generation in this PR.

• [x] Put exercises within chapters in a pdf, mark Pretty Printing as Extra, make Solutions a separate chapter

  From → to

  

• [x] Enable pdf generation in PRs

  Explanation: like Julian mentioned, there are 2 ways to generate a pdf - via actions/upload-artifact (makes it possible to download an artifact [from the artifacts section in actions tab] in a zip file; and then unzip it; and then see the pdf) and via marvinpinto/action-automatic-releases (automatically creates a release on each push, and makes the pdf directly available via that release).

  This PR makes it so that we do marvinpinto/action-automatic-releases when we push to master, and actions/upload-artifact when we push to any other branch (so that we can check out the generated pdf).

Gotchas

I can now see the generated pdf in my forked branch, however the new workflow doesn't run in this repo for some reason. Maybe this will work upon the creation of further PRs after this is merged, or maybe some permission needs to be set by Arthur, will be more clear on further PRs.

[arthurpaulino]

This is really amazing. Thank you very much!