HTML5: Fix minification error with Emscripten 1.39.9

It used an old vendored version of acorn.js which seems to choke on this
trailing comma. This is not a problem for more recent Emscripten versions.

We disable the `comma-dangle` check in ESLint to prevent this issue.

platform/javascript/.eslintrc.js

@@ -39,5 +39,13 @@ module.exports = {
 		// Closure compiler (exported properties)
 		"quote-props": ["error", "consistent"],
 		"dot-notation": "off",
+		// No comma dangle for functions (it's madness, and ES2017)
+		"comma-dangle": ["error", {
+			"arrays": "always-multiline",
+			"objects": "always-multiline",
+			"imports": "always-multiline",
+			"exports": "always-multiline",
+			"functions": "never"
+		}],
 	}
 };