v8.21.0

Features

• 7b43ea1 feat: Implement FlatESLint (#16149) (Nicholas C. Zakas)
• 92bf49a feat: improve the key width calculation in key-spacing rule (#16154) (Nitin Kumar)
• c461542 feat: add new allowLineSeparatedGroups option to the sort-keys rule (#16138) (Nitin Kumar)
• 1cdcbca feat: add deprecation warnings for legacy API in RuleTester (#16063) (Nitin Kumar)

Bug Fixes

• 0396775 fix: lines-around-comment apply allowBlockStart for switch statements (#16153) (Nitin Kumar)

Documentation

• 2aadc93 docs: add anchors to headings inside docs content (#16134) (Strek)

Chores

• 8892511 chore: Upgrade to Espree 9.3.3 (#16173) (Brandon Mills)
• 1233bee chore: switch to eslint-plugin-node's maintained fork (#16150) (唯然)
• 97b95c0 chore: upgrade puppeteer v13 (#16151) (唯然)