Recommend using BlackConnect in IntelliJ IDEs (#3150)

* Recommend using BlackConnect in IntelliJ IDEs

* IntelliJ IDEs integration docs: improve formatting

* Add changelog for recommending BlackConnect

* IntelliJ IDEs integration docs: improve formatting

* Apply suggestions from code review

Co-authored-by: Richard Si <63936253+ichard26@users.noreply.github.com>

* Fix indentation

* Apply italic to Black name

Consequently with other places in the document

* Move CHANGELOG entry to Unreleased section

* IntelliJ IDEs integration docs: bring back a point with formatting a file

* IntelliJ IDEs integration docs: fix extra whitespace and linebreak

Co-authored-by: Richard Si <63936253+ichard26@users.noreply.github.com>