dev-plugins: Improve formatting of reviewer suggestion documentation
dev-plugins: Improve formatting of reviewer suggestion documentation

- Add backticks around code
- Add line breaks to split the wall-of-text into logical paragraphs
- Reword the paragraph about configuring the plugin weight

Change-Id: Ic9997036c94ef2fc0e46a1ff62fa8c42c7ef7fc2

qtproject/qtqa-gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit