Migrate to ESLint 9 (#6685)

* Migrate to ESLint 9
* https://eslint.org/docs/latest/use/migrate-to-9.0.0
* https://eslint.style/guide/migration
* https://github.com/neostandard/neostandard/ (https://github.com/standard/standard/issues/1948)

fix broken Dependabot PRs such as https://github.com/FreshRSS/FreshRSS/pull/6680

* comma-dangle rule is already included

* Use more standard filename

* More flexible syntax globals

* resolveIgnoresFromGitignore

* Dependabog update

* Relax object-shorthand

* GitHub action node-version

* GitHub action node-version again

* object-shorthand: off

* node >=18 due to dependencies

1 files changed, 55 insertions, 0 deletions

diff --git a/eslint.config.js b/eslint.config.js
new file mode 100644
index 000000000..c65f7520c
--- /dev/null
+++ b/eslint.config.js
@@ -0,0 +1,55 @@
+import globals from "globals";
+import js from "@eslint/js";
+import neostandard, { resolveIgnoresFromGitignore } from 'neostandard';
+import stylistic from '@stylistic/eslint-plugin';
+
+export default [
+	{
+		files: ["**/*.js"],
+		languageOptions: {
+			globals: {
+				...globals.browser,
+			},
+			sourceType: "script",
+		},
+	},
+	{
+		ignores: [
+			...resolveIgnoresFromGitignore(),
+			"**/*.min.js",
+			"extensions/",
+			"p/scripts/vendor/",
+		],
+	},
+	js.configs.recommended,
+	// stylistic.configs['recommended-flat'],
+	...neostandard(),
+	{
+		plugins: {
+			"@stylistic": stylistic,
+		},
+		rules: {
+			"camelcase": "off",
+			"eqeqeq": "off",
+			"no-empty": ["error", { "allowEmptyCatch": true }],
+			"no-unused-vars": ["error", {
+				"args": "none",
+				"caughtErrors": "none",
+			}],
+			"object-shorthand": "off",
+			"yoda": "off",
+			"@stylistic/indent": ["warn", "tab", { "SwitchCase": 1 }],
+			"@stylistic/linebreak-style": ["error", "unix"],
+			"@stylistic/max-len": ["warn", 165],
+			"@stylistic/no-tabs": "off",
+			"@stylistic/quotes": ["off", "single", { "avoidEscape": true }],
+			"@stylistic/quote-props": ["warn", "consistent"],
+			"@stylistic/semi": ["warn", "always"],
+			"@stylistic/space-before-function-paren": ["warn", {
+				"anonymous": "always",
+				"asyncArrow": "always",
+				"named": "never",
+			}],
+		},
+	},
+];