add average frequency tag

[tadorituki]

this is a draft.
added a tag that displays the harmonic mean of the frequency ranks
updated a few things from #1303

[codspeed-hq]

CodSpeed Performance Report

Merging #1479 will not alter performance

_{Comparing tadorituki:tadoru (736dbcd) with master (4f109a9)}

Summary

✅ 5 untouched benchmarks

[tadorituki]

this is ready for merge, please review

[github-actions]

⚠️ Visual changes detected by playwright; please check the report to verify if they are desirable.

[tadorituki]

fixed issues with unit tests, now ready to merge

[Kuuuube]

Add a settings update for this here: https://github.com/yomidevs/yomitan/blob/master/ext/js/data/options-util.js
And bump the version here: https://github.com/yomidevs/yomitan/blob/master/test/options-util.test.js

[Kuuuube]

It's probably also a good idea to split out the average calculation from the groupTermFrequencies function. Maybe just have a call to a different function inside the groupTermFrequencies that adds on to the data or whatever it needs to do.

[djahandarie]

@tadorituki Do you have time to make changes to get this merged?

[tadorituki]

ready to merge. i think

[Kuuuube]

Did some refactoring of this myself. This should be good now.

[Kuuuube]

Since I'm the last committer, I cannot merge this myself. Will need another approval.