Update lint configs (#4)

This updates all files to match the MetaMask code style. I've updated
the ESLint, Prettier, and TypeScript configs, and fixed all lint errors.

.depcheckrc.json

@@ -0,0 +1,12 @@
+{
+  "ignores": [
+    "@lavamoat/allow-scripts",
+    "@lavamoat/preinstall-always-fail",
+    "@metamask/auto-changelog",
+    "@types/*",
+    "prettier-plugin-packagejson",
+    "superstruct",
+    "ts-node",
+    "typedoc"
+  ]
+}

.editorconfig

@@ -7,4 +7,3 @@ end_of_line = lf
 charset = utf-8
 trim_trailing_whitespace = true
 insert_final_newline = true
-max_line_length = 80

.eslintrc.js

@@ -0,0 +1,45 @@
+module.exports = {
+  root: true,
+
+  extends: ['@metamask/eslint-config'],
+
+  overrides: [
+    {
+      files: ['*.ts'],
+      extends: ['@metamask/eslint-config-typescript'],
+    },
+
+    {
+      files: ['*.js'],
+      parserOptions: {
+        sourceType: 'script',
+      },
+      extends: ['@metamask/eslint-config-nodejs'],
+    },
+
+    {
+      files: ['*.test.ts', '*.test.js'],
+      extends: [
+        '@metamask/eslint-config-jest',
+        '@metamask/eslint-config-nodejs',
+      ],
+      rules: {
+        '@typescript-eslint/no-shadow': [
+          'error',
+          {
+            allow: ['describe', 'it'],
+          },
+        ],
+      },
+    },
+  ],
+
+  ignorePatterns: [
+    '!.eslintrc.js',
+    '!.prettierrc.js',
+    'dist/',
+    'docs/',
+    '.yarn/',
+    'examples/',
+  ],
+};

.gitignore

@@ -4,6 +4,9 @@ npm-debug.log
 package-lock.json
 tmp/
 
+# Optional eslint cache
+.eslintcache
+
 # yarn v3 (w/o zero-install)
 # See: https://yarnpkg.com/getting-started/qa#which-files-should-be-gitignored
 .pnp.*

.prettierrc.js

@@ -0,0 +1,8 @@
+// All of these are defaults except singleQuote, but we specify them
+// for explicitness
+module.exports = {
+  quoteProps: 'as-needed',
+  singleQuote: true,
+  tabWidth: 2,
+  trailingComma: 'all',
+};