Renovate[bot]: Update dependency grunt-eslint to v25 (#1389)

* Renovate[bot]: Update dependency grunt-eslint to v25

* Migrate to flat eslint config

---------

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: mattyrob <mattyrobuk@gmail.com>

.eslint.config.js

@@ -0,0 +1,49 @@
+module.exports = [
+	{
+		"languageOptions": {
+			"ecmaVersion": 6
+		},
+		"rules": {
+			"block-scoped-var": "error",
+			"comma-dangle": "error",
+			"comma-style": [
+				"error", "last"
+			],
+			"eol-last": [
+				"error",
+				"always"
+			],
+			"func-style": [
+				"error",
+				"declaration",
+				{
+					"allowArrowFunctions": false
+				}
+			],
+			"linebreak-style": [
+				"error",
+				"unix"
+			],
+			"no-confusing-arrow": "error",
+			"no-cond-assign": "off",
+			"no-empty": "off",
+			"no-eval": "error",
+			"no-extra-boolean-cast": "off",
+			"no-implied-eval": "error",
+			"no-misleading-character-class": "off",
+			"no-mixed-spaces-and-tabs": "off",
+			"no-prototype-builtins": "off",
+			"no-redeclare": "off",
+			"no-shadow-restricted-names": "off",
+			"no-trailing-spaces": "error",
+			"no-undef": "off",
+			"no-unused-vars": "off",
+			"no-useless-escape": "off",
+			"semi": [
+				"error",
+				"always"
+			],
+			"semi-spacing": "error"
+		}
+	}
+];

Gruntfile.js

@@ -556,6 +556,9 @@ module.exports = function(grunt) {
 			}
 		},
 		eslint: {
+			options: {
+				overrideConfigFile: '.eslint.config.js'
+			},
 			grunt: {
 				src: [
 					'Gruntfile.js'