Revise Persisting store data doc page (#1497)

* docs(#1220): revise persisting-store-data page

- add cross-links
- add line breaks for easier Markdown reading
- unify Persist middleware spelling
- change fishes to bears, because the plural of fish is fish,
  and it would be less readable
- make sentences more concise

* docs(#1220): make the sentences more concise

* docs(#1220): unify formatting of methods