Remove support for IE11 and dead browsers

Handlebars v5 will target modern browsers,
while older browsers will still receive support
via version 4.x.

README.markdown

@@ -79,17 +79,16 @@ There are a few Mustache behaviors that Handlebars does not implement.
 Supported Environments
 ----------------------
 
-Handlebars has been designed to work in any ECMAScript 3 environment. This includes
+Handlebars has been designed to work in any ECMAScript 7 (2016) environment. This includes
 
-- Node.js 12+
+- Node.js
 - Chrome
 - Firefox
-- Safari 5+
-- Opera 11+
-- IE 6+
+- Safari
+- Edge
+
+If you need to support older environments, use Handlebars version 4.
 
-Older versions and other runtimes are likely to work but have not been formally
-tested. The compiler requires `JSON.stringify` to be implemented natively or via a polyfill. If using the precompiler this is not necessary.
 
 Performance
 -----------

package.json

@@ -43,7 +43,6 @@
     "eslint": "^6.7.2",
     "eslint-config-prettier": "^6.7.0",
     "eslint-plugin-compat": "^3.13.0",
-    "eslint-plugin-es5": "^1.4.1",
     "fs-extra": "^8.1.0",
     "grunt": "^1.0.4",
     "grunt-babel": "^5.0.0",
@@ -113,6 +112,13 @@
     "types/*.d.ts",
     "runtime.d.ts"
   ],
+  "browserslist": [
+    "last 2 versions",
+    "Firefox ESR",
+    "not dead",
+    "not IE 11",
+    "maintained node versions"
+  ],
   "husky": {
     "hooks": {
       "pre-commit": "lint-staged"

spec/.eslintrc

@@ -1,12 +1,5 @@
 {
-  "extends": [
-    "../.eslintrc.js",
-    "plugin:es5/no-es2015",
-    "prettier"
-  ],
-  "plugins": [
-    "es5"
-  ],
+  "extends": ["../.eslintrc.js"],
   "globals": {
     "CompilerContext": true,
     "Handlebars": true,
@@ -16,8 +9,6 @@
     "shouldThrow": true,
     "expectTemplate": true,
     "compileWithPartials": true,
-    "console": true,
-    "require": true,
     "suite": true,
     "equal": true,
     "equals": true,

tests/integration/multi-nodejs-test/.eslintrc.js

@@ -1,5 +1,5 @@
 module.exports = {
-  extends: ['eslint:recommended', 'plugin:es5/no-es2015', 'prettier'],
+  extends: ['eslint:recommended', 'prettier'],
   globals: {
     self: false
   },