Distribute ES module

- Use RollupJS and Terser for bundling
- Bumped up dev dependency versions
- Bumped up Travis NodeJS version matrix
- Refactored Papa worker identification
- Refactored worker logic to use `import.meta.url` or `document.currentScript.src`
mholt#748
mholt#813

.eslintrc.js

@@ -1,6 +1,7 @@
 module.exports = {
 	"parserOptions": {
-		"ecmaVersion": 5
+		"ecmaVersion": 2020,
+		"sourceType": "module"
 	},
 	"env": {
 		"browser": true,

.travis.yml

@@ -1,6 +1,7 @@
 language: node_js
 node_js:
-  - "8"
-  - "9"
   - "10"
-  - "11"
+  - "12"
+  - "14"
+  - "15"
+  - "16"

package.json

@@ -34,21 +34,26 @@
 		"url": "https://twitter.com/mholt6"
 	},
 	"license": "MIT",
-	"main": "papaparse.js",
-	"browser": "papaparse.min.js",
+	"main": "./papaparse.js",
+	"browser": "./papaparse.min.js",
+	"exports": {
+		"import": "./papaparse.mjs",
+		"require": "./papaparse.js"
+	},
 	"devDependencies": {
-		"chai": "^4.2.0",
-		"connect": "^3.3.3",
-		"eslint": "^4.19.1",
-		"grunt": "^1.0.2",
-		"grunt-contrib-uglify": "^3.3.0",
-		"mocha": "^5.2.0",
-		"mocha-headless-chrome": "^2.0.1",
-		"open": "7.0.0",
-		"serve-static": "^1.7.1"
+		"chai": "^4.3.4",
+		"connect": "^3.7.0",
+		"eslint": "^7.28.0",
+		"mocha": "^9.0.0",
+		"mocha-headless-chrome": "^3.1.0",
+		"open": "8.2.0",
+		"rollup": "^2.51.1",
+		"rollup-plugin-terser": "^7.0.2",
+		"serve-static": "^1.14.1"
 	},
 	"scripts": {
-		"lint": "eslint --no-ignore papaparse.js Gruntfile.js .eslintrc.js 'tests/**/*.js'",
+		"build": "rollup -c rollup.config.mjs",
+		"lint": "eslint --no-ignore papaparse.mjs .eslintrc.js 'tests/**/*.js'",
 		"test-browser": "node tests/test.js",
 		"test-mocha-headless-chrome": "node tests/test.js --mocha-headless-chrome",
 		"test-node": "mocha tests/node-tests.js tests/test-cases.js",