Add basic ESLint configuration for formatting

This doesn't enable any of ESLint's actual possible-issue linting,
but just style normalization based on the Prettier configuration (but without line length limits).

.eslintignore

@@ -0,0 +1,4 @@
+extensions
+extensions-disabled
+repositories
+venv

.eslintrc.js

@@ -0,0 +1,49 @@
+module.exports = {
+    env: {
+        browser: true,
+        es2021: true,
+    },
+    // "extends": "eslint:recommended",
+    parserOptions: {
+        ecmaVersion: "latest",
+    },
+    rules: {
+        "arrow-spacing": "error",
+        "block-spacing": "error",
+        "brace-style": "error",
+        "comma-dangle": ["error", "only-multiline"],
+        "comma-spacing": "error",
+        "comma-style": ["error", "last"],
+        "curly": ["error", "multi-line", "consistent"],
+        "eol-last": "error",
+        "func-call-spacing": "error",
+        "function-call-argument-newline": ["error", "consistent"],
+        "function-paren-newline": ["error", "consistent"],
+        "indent": ["error", 4],
+        "key-spacing": "error",
+        "keyword-spacing": "error",
+        "linebreak-style": ["error", "unix"],
+        "no-extra-semi": "error",
+        "no-mixed-spaces-and-tabs": "error",
+        "no-trailing-spaces": "error",
+        "no-whitespace-before-property": "error",
+        "object-curly-newline": ["error", {consistent: true, multiline: true}],
+        "quote-props": ["error", "consistent-as-needed"],
+        "semi": ["error", "always"],
+        "semi-spacing": "error",
+        "semi-style": ["error", "last"],
+        "space-before-blocks": "error",
+        "space-before-function-paren": ["error", "never"],
+        "space-in-parens": ["error", "never"],
+        "space-infix-ops": "error",
+        "space-unary-ops": "error",
+        "switch-colon-spacing": "error",
+        "template-curly-spacing": ["error", "never"],
+        "unicode-bom": "error",
+        // "no-multi-spaces": "error", // TODO: enable?
+        // "object-curly-spacing": "off", // TODO: enable?
+        // "object-property-newline": "off", // TODO: enable?
+        // "operator-linebreak": "off", // TODO: enable?
+        // "quotes": ["error", "double", {avoidEscape: true}],  // TODO: enable?
+    },
+};

.gitignore

@@ -34,3 +34,5 @@ notification.mp3
 /test/stderr.txt
 /cache.json*
 /config_states/
+/node_modules
+/package-lock.json

package.json

@@ -0,0 +1,11 @@
+{
+  "name": "stable-diffusion-webui",
+  "version": "0.0.0",
+  "devDependencies": {
+    "eslint": "^8.40.0"
+  },
+  "scripts": {
+    "lint": "eslint .",
+    "fix": "eslint --fix ."
+  }
+}