fix: replaced overly complicated redirection rules with a simple hack

[baszalmstra]

This PR replaces the overly complex logic to make the documentation for v0.2 available under a subdirectory.

Instead of adding a base tag to the documentation this PR adds some simple javascript to add a trailing slash to a url if the url doesnt end in .html. That should fix our relative path issues.

It also removes the need for mdbook v0.4 so I reverted back to just downloading the binary. That should make our CI mucho faster.

As an added bonus I also added a github icon that links back this repo.

We also have to push these changes to release/v0.2.

Closes #195
Closes #190

[codecov]

Codecov Report

Merging #196 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #196   +/-   ##
=======================================
  Coverage   82.94%   82.94%           
=======================================
  Files         163      163           
  Lines       11509    11509           
=======================================
  Hits         9546     9546           
  Misses       1963     1963           

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