List of most frequent bigrams/trigrams

**Is your feature request related to a problem? Please describe.**
We have an overview of most frequent bigrams / trigrams *including a search term* implemented, but for comparison with word embeddings, it might be interesting for users to also consult a table of the most frequent bigrams and trigrams in general.

**Describe the solution you'd like**
This could be achieved through [sklearn's CountVectorizer[(https://scikit-learn.org/stable/modules/generated/sklearn.feature_extraction.text.CountVectorizer.html), but we might also consider other measures than frequency, consider [this nltk tutorial](https://www.nltk.org/howto/collocations). The question is whether we want to offer one static list, or instead generate lists on the fly, based on a filtered set of documents.

**Additional context**
The feature request does seem to be for a table, not a visualization, so facets for time windows are not needed.

No files, tests, or entry points are named in the issue. Start by locating the existing overview of frequent bigrams and trigrams with a search term, then compare CountVectorizer with the linked NLTK collocations approach; done means a table of general bigrams and trigrams is available, with static versus filtered or on-the-fly behavior decided.

Written by the indexing model from the issue text.