Leonenko-Prozano-Savani differential estimator for `Shannon`, `Renyi` and `Tsallis` entropies

[kahaaga]

The title is descriptive enough. I'm cleaning up some todos in CausalityTools, and this estimator is one of those that got left behind when we did the first major refactoring of ComplexityMeasures.jl. Here it is, in all its multiple-entropies estimatory glory.

The docs are here.

Changes:

• Added new LeonenkoProzantoSavani differential estimator, with implementations for Shannon, Renyi and Tsallis entropies.
• Added analytical tests for all three types of entropy, testing that we're within 10% of the target entropy for a multivariate normal distribution.
• Added documentation examples for the estimation of Shannon, Renyi and Tsallis differential entropies (also using multivariate normal with known entropies).

[codecov[bot]]

Codecov Report

Merging #310 (b0ef203) into main (35e9522) will increase coverage by 0.26%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #310      +/-   ##
==========================================
+ Coverage   87.49%   87.76%   +0.26%     
==========================================
  Files          75       76       +1     
  Lines        1879     1920      +41     
==========================================
+ Hits         1644     1685      +41     
  Misses        235      235              

Files Changed	Coverage Δ
src/core/information_measures.jl	0.00% <ø> (ø)
..._estimators/nearest_neighbors/nearest_neighbors.jl	100.00% <ø> (ø)
...mators/nearest_neighbors/LeonenkoProzantoSavani.jl	100.00% <100.00%> (ø)

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