Update eslint monorepo to v9.21.0 (minor)

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
@eslint/js (source)	9.18.0 -> 9.21.0
eslint (source)	9.18.0 -> 9.21.0

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Release Notes

eslint/eslint (@​eslint/js)

v9.21.0

Compare Source

Features

• 418717f feat: introduce new deprecated types for rules (#​19238) (fnx)
• 5c5b802 feat: Add --ext CLI option (#​19405) (Milos Djermanovic)

Bug Fixes

• db5340d fix: update missing plugin message template (#​19445) (Milos Djermanovic)
• d8ffdd4 fix: do not exit process on rule crash (#​19436) (Francesco Trotta)

Documentation

• c5561ea docs: Update README (GitHub Actions Bot)
• 80b0485 docs: replace var with let and const in rule example (#​19434) (Tanuj Kanti)
• f67d5e8 docs: Update README (GitHub Actions Bot)
• 75afc61 docs: Update README (GitHub Actions Bot)
• 0636cab docs: Update Eleventy from v2 to v3 (#​19415) (Amaresh S M)
• dd7d930 docs: Update README (GitHub Actions Bot)

Chores

• a8c9a9f chore: update @eslint/eslintrc and @eslint/js (#​19453) (Francesco Trotta)
• 265e0cf chore: package.json update for @​eslint/js release (Jenkins)
• 3401b85 test: add test for Rule.ReportDescriptor type (#​19449) (Francesco Trotta)
• e497aa7 chore: update rewrite dependencies (#​19448) (Francesco Trotta)
• dab5478 chore: better error message for missing plugin in config (#​19402) (Tanuj Kanti)
• ebfe2eb chore: set js language for bug report issue config block (#​19439) (Josh Goldberg ✨)
• 5fd211d test: processors can return subpaths (#​19425) (Milos Djermanovic)

v9.20.0

Compare Source

Features

• e89a54a feat: change behavior of inactive flags (#​19386) (Milos Djermanovic)

Bug Fixes

• 91d4d9f fix: Bring types in sync with @​eslint/core (#​19157) (Nicholas C. Zakas)
• fa25c7a fix: Emit warning when empty config file is used (#​19399) (Nicholas C. Zakas)
• 31a9fd0 fix: Clearer error message for wrong plugin format (#​19380) (Nicholas C. Zakas)
• 61d99e3 fix: Better error message for unserializable parser (#​19384) (Nicholas C. Zakas)
• db1b9a6 fix: Ensure module scope is checked for references in consistent-this (#​19383) (Nicholas C. Zakas)
• 8bcd820 fix: arrow-body-style crash with single-token body (#​19379) (Milos Djermanovic)

Documentation

• b7012c8 docs: rewrite examples with var using let and const (#​19407) (Mueez Javaid Hashmi)
• 6406376 docs: Update README (GitHub Actions Bot)
• 350f2b9 docs: rewrite some examples with var using let and const (#​19404) (Mueez Javaid Hashmi)
• 93c325a docs: rewrite examples with var using let and const (#​19398) (Mueez Javaid Hashmi)
• 56ff404 docs: replace var with let or const in rules docs (#​19396) (Daniel Harbrueger)
• 4053226 docs: change sourceType in no-eval examples (#​19393) (Milos Djermanovic)
• 1324af0 docs: replace var with let and const in rules docs (#​19392) (Daniel Harbrueger)
• 8b87e00 docs: replace var with const and let in rules (#​19389) (Tanuj Kanti)
• 758c66b docs: Explain what frozen rules mean (#​19382) (Nicholas C. Zakas)
• 0ef8bb8 docs: additional checks for rule examples (#​19358) (Milos Djermanovic)
• 58ab2f6 docs: fix order of installation steps in getting started (#​19326) (Tanuj Kanti)

Chores

• 979097a chore: upgrade @​eslint/js@​9.20.0 (#​19412) (Francesco Trotta)
• 031734e chore: package.json update for @​eslint/js release (Jenkins)
• d4c47c3 test: avoid empty config warning in test output (#​19408) (Milos Djermanovic)
• 67dd82a chore: update dependency @​eslint/json to ^0.10.0 (#​19387) (renovate[bot])
• 15ac0e1 chore: add permissions: read-all to stale.yml workflow (#​19374) (Josh Goldberg ✨)

v9.19.0

Compare Source

Features

• 1637b8e feat: add --report-unused-inline-configs (#​19201) (Josh Goldberg ✨)

Bug Fixes

• aae6717 fix: sync rule type header comments automatically (#​19276) (Francesco Trotta)

Documentation

• cfea9ab docs: Clarify overrideConfig option (#​19370) (Nicholas C. Zakas)
• 2b84f66 docs: Update README (#​19362) (Nicholas C. Zakas)
• 044f93c docs: clarify frozen rule description (#​19351) (Pavel)
• 797ee7c docs: fix Bluesky links (#​19368) (Milos Djermanovic)
• 81a9c0e docs: Update README (GitHub Actions Bot)
• 093fb3d docs: replace var with let and const in rule examples (#​19365) (Tanuj Kanti)
• 417de32 docs: replace var with const in rule examples (#​19352) (jj)
• 17f2aae docs: update getting-started config to match default generated config (#​19308) (0xDev)
• 8a0a5a8 docs: better global ignores instruction (#​19297) (Jacopo Marrone)
• 6671a2c docs: Update README (GitHub Actions Bot)
• e39d3f2 docs: fix divider for rule category (#​19264) (Tanuj Kanti)
• e0cf53f docs: fix search result box position for small screens (#​19328) (Tanuj Kanti)
• f92a680 docs: replace var with let or const in rule examples (#​19331) (Ravi Teja Kolla)
• b04b84b docs: revert accidental changes in TS config files docs (#​19336) (Francesco Trotta)

Chores

• 9b9cb05 chore: upgrade @​eslint/js@​9.19.0 (#​19371) (Milos Djermanovic)
• 58560e7 chore: package.json update for @​eslint/js release (Jenkins)
• 2089707 test: fix failing test in Node.js v22.13.0 (#​19345) (Francesco Trotta)

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