feat(esm): upgrade to be a pure ESM package

BREAKING CHANGE: This package is now only available
via ESM. This means it only supports Node 12+ too.

+ Updated dependancies to use ESM versions
+ Various changes for ESM

.eslintignore

@@ -0,0 +1 @@
+node_modules/

.eslintrc.json

@@ -0,0 +1,16 @@
+{
+  "env": {
+    "node": true,
+    "es2021": true,
+    "jest/globals": true
+  },
+  "extends": ["eslint:recommended", "prettier", "plugin:node/recommended"],
+  "plugins": ["prettier", "jest"],
+  "parserOptions": {
+    "ecmaVersion": 12
+  },
+  "rules": {
+    "prettier/prettier": ["error"],
+    "no-console": ["error"]
+  }
+}

.npmignore

@@ -0,0 +1 @@
+test/

index.js

@@ -1,3 +1,3 @@
-const letterboxd = require("./src/letterboxd");
+import letterboxd from "./src/letterboxd.js";
 
-module.exports = letterboxd;
+export default letterboxd;