ESLint support (#1119)

* eslint integration

* configure the rules and warnings

* update ci script

.eslintignore

@@ -0,0 +1,8 @@
+# don't ever lint node_modules
+node_modules
+# don't lint build output (make sure it's set to your correct build folder name)
+dist
+# don't lint nyc coverage output
+coverage
+
+test/performance

.eslintrc.js

@@ -0,0 +1,32 @@
+module.exports = {
+    root: true,
+    env: {
+        node: true,
+        browser: true
+    },
+    parser: '@typescript-eslint/parser',
+    plugins: [
+      '@typescript-eslint',
+    ],
+    extends: [
+      'eslint:recommended',
+      'plugin:@typescript-eslint/recommended',
+    ],
+    // TODO: consider removing these rules and improving the source code
+    rules: {
+        'prefer-const': 1,
+        'no-useless-escape': 1,
+        'prefer-rest-params': 1,
+        'prefer-spread': 1,
+        'no-prototype-builtins': 1,
+        '@typescript-eslint/explicit-module-boundary-types': 1,
+        '@typescript-eslint/ban-ts-comment': 1,
+        '@typescript-eslint/ban-types': 1,
+        '@typescript-eslint/no-var-requires': 1,
+        '@typescript-eslint/no-explicit-any': 1,
+        '@typescript-eslint/no-empty-function': 1,
+        '@typescript-eslint/no-namespace': 1,
+        '@typescript-eslint/no-inferrable-types': 1,
+        '@typescript-eslint/no-unused-vars': 1
+    }
+  };