feat!: use eslint instead of tslint (#400)

BREAKING CHANGE: Switch from tslint to eslint. This will impact all lint rules, and tslint specific configuration.

.cirrus.yml

@@ -1,5 +1,5 @@
 container:
-  image: node:10
+  image: node:12
 
 windows_task:
   windows_container:
@@ -16,11 +16,19 @@ lint_task:
   install_script: npm ci
   test_script: npm run lint
 
+license_task:
+  install_script: npm ci
+  test_script: npm run license-check
+
+system_test_task:
+  install_script: npm ci
+  test_script: npm run system-test
+
 test_task:
   container:
     matrix:
+      image: node:13
       image: node:12
-      image: node:11
       image: node:10
       image: node:8
   install_script: npm ci

.eslintignore

@@ -0,0 +1,2 @@
+build/
+test/fixtures/

.eslintrc.json

@@ -0,0 +1,42 @@
+{
+  "extends": [
+    "eslint:recommended",
+    "plugin:node/recommended",
+    "prettier"
+  ],
+  "plugins": [
+    "node",
+    "prettier"
+  ],
+  "rules": {
+    "prettier/prettier": "error",
+    "block-scoped-var": "error",
+    "eqeqeq": "error",
+    "no-warning-comments": "warn",
+    "no-var": "error",
+    "prefer-const": "error"
+  },
+  "overrides": [
+    {
+      "files": "**/*.ts",
+      "parser": "@typescript-eslint/parser",
+      "extends": [
+        "plugin:@typescript-eslint/recommended"
+      ],
+      "rules": {
+        "@typescript-eslint/no-non-null-assertion": "off",
+        "node/no-missing-import": "off",
+        "node/no-unsupported-features/es-syntax": "off",
+        "@typescript-eslint/explicit-function-return-type": "off",
+        "@typescript-eslint/camelcase": "off",
+        "node/no-missing-require": "off",
+        "no-dupe-class-members": "off",
+        "node/shebang": "off"
+      },
+      "parserOptions": {
+        "ecmaVersion": 2018,
+        "sourceType": "module"
+      }
+    }
+  ]
+}

README.md

@@ -16,7 +16,7 @@ To borrow from [standardjs][standardjs-url]:
 - **Catch style issues & programmer errors early**. Save precious code review time by eliminating back-and-forth between reviewer & contributor.
 - **Opinionated, but not to a fault**. We recommend you use the default configuration, but if you *need* to customize compiler or linter config, you can.
 
-Under the covers, we use [tslint][tslint-url] to enforce the style guide and provide automated fixes, and [prettier][prettier-url] to re-format code.
+Under the covers, we use [eslint][eslint-url] to enforce the style guide and provide automated fixes, and [prettier][prettier-url] to re-format code.
 
 ## Getting Started
 
@@ -77,4 +77,4 @@ Made with ❤️ by the Google Node.js team.
 [snyk-image]: https://snyk.io/test/github/google/gts/badge.svg
 [snyk-url]: https://snyk.io/test/github/google/gts
 [standardjs-url]: https://www.npmjs.com/package/standard
-[tslint-url]: https://palantir.github.io/tslint/
+[eslint-url]: https://eslint.org/