Small erorrs in docs validate links

[jaksle]

I've noticed two broken links. This corrects them. Additionally, in the plots in the same sections titles overlap with x labels which makes them unintelligible. But, compiling the same docs on my machine does not replicate this behaviour. I have Plots v1.39.0.

EDIT. I remade this PR, I had problems with synchronising fork to the origin.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b4df21a) 95.40% compared to head (c62cfc2) 95.40%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #270   +/-   ##
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  Coverage   95.40%   95.40%           
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  Files          20       20           
  Lines        1503     1503           
=======================================
  Hits         1434     1434           
  Misses         69       69           

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[alyst]

Thanks! The changes look straightforward, but there are conflicts with the master. It looks like you still have some mix-ups in the commits of this PR: there are 95 commits, which is a bit too much for 3 changed lines.
I guess the easiest would be if you just create a new branch off the Clustering.jl master and add a single new commit with the fixes to the ref links.
And in general, I think it is a good practice, when working on a PR, to create a new feature branch in your local repository instead of committing directly to the main (master one).

Note that for #257 I've squashed all your commits together (since it was all about adding new code) and force-pushed it (to the PR branch in your repository, which happened to be master), so that the commit history in the Clustering.jl is cleaner.

[alyst]

BTW, do you have a quick fix for the overlapping titles issue in the quality indices docs?
I guess it is just about increasing the vertical padding/margins of the subplots. Would be nice to have it in this PR.