Add plotting

[mikeheddes]

Add two utility functions that will generate a similarity plot. There first one gets the similarity characteristics of a basis hypervector set. The second shows the similarity of one hypervector with a set.

• Set characteristics
• Hypervector with set similarities

[dheyay]

The hypervectors with set similarity should be able to take a vector and a set?
Or in line with the fruit example, we take the vector and set(s), bind together and find similarity with all sets(memory) ?

[mikeheddes]

For the hypervector with set you just plot the similarity of one hypervector with a set of hypervectors, like this:

memory = torchhd.random_hv(8, 10000)
similarity = torchhd.functional.cosine_similarity(memory[0], memory)
# plot the similarity with matplotlib using the stem

Docs: plt.stem