Quick scan readability data should be rendered by LIX metrics

Problem/Motivation

Currently Readability section is display the results, description and summary as per Flesch-Kincaid
Update the Acquia Optimize extension quick scan - Readability result as per below metric

Proposed resolution

LIX metrics
>55 Very difficult, academic-level non-fiction, legal texts.

45-54 Difficult, e.g. non-fiction books, popular science works, academic publications.

35-44 Medium, e.g. newspapers and magazines.

25-34 Easy for advanced readers, e.g. weekly magazine literature and fiction for adults.

<=24 Easy text for all readers, e.g. children's literature.

Remaining tasks

User interface changes

API changes

Data model changes