Build: Add `exports` to package.json, export slim & esm builds

Summary of the changes:
* define the `exports` field in `package.json`; `jQuery` & `$` are also
  exported as named exports in ESM builds now
* declare `"type": "module"` globally except for the `build` folder
* add the `--esm` option to `grunt custom`, generating jQuery as an ECMAScript
  module into the `dist-module` folder
* expand `node_smoke_tests` to test the slim & ESM builds and their various
  combinations; also, test both jQuery loaded via a path to the file as well
  as from module specifiers that should be parsed via the `exports` feature
* add details about ESM usage to the release package README
* run `compare_size` on all built minified files; don't run it anymore on
  unminified files where they don't provide lots of value
* remove the remove_map_comment task; SWC doesn't insert the
`//# sourceMappingURL=` pragma by default so there's nothing to strip

Fixes gh-4592
Closes gh-5255

3 files changed, 66 insertions, 0 deletions

diff --git a/src/.eslintrc.json b/src/.eslintrc.json
index f1b596dff..c2b08fb93 100644
--- a/src/.eslintrc.json
+++ b/src/.eslintrc.json
@@ -58,6 +58,30 @@
 		},
 
 		{
+			"files": "wrapper-esm.js",
+			"parserOptions": {
+				"ecmaVersion": 2015,
+				"sourceType": "module"
+			},
+			"globals": {
+				"jQuery": false
+			},
+			"rules": {
+				"no-unused-vars": "off",
+				"indent": [ "error", "tab", {
+					// Unlike other codes, "wrapper.js" is implemented in UMD.
+					// So it required a specific exception for jQuery's UMD
+					// Code Style. This makes that indentation check is not
+					// performed for 1 depth of outer FunctionExpressions
+					"ignoredNodes": [
+						"Program > FunctionDeclaration > *"
+					]
+				} ],
+				"import/no-unused-modules": "off"
+			}
+		},
+
+		{
 			"files": "exports/amd.js",
 			"globals": {
 				"define": false
diff --git a/src/wrapper-esm.js b/src/wrapper-esm.js
new file mode 100644
index 000000000..00ff2995c
--- /dev/null
+++ b/src/wrapper-esm.js
@@ -0,0 +1,41 @@
+/*!
+ * jQuery JavaScript Library v@VERSION
+ * https://jquery.com/
+ *
+ * Copyright OpenJS Foundation and other contributors
+ * Released under the MIT license
+ * https://jquery.org/license
+ *
+ * Date: @DATE
+ */
+// For ECMAScript module environments where a proper `window`
+// is present, execute the factory and get jQuery.
+// For environments that do not have a `window` with a `document`
+// (such as Node.js), expose a factory as module.exports.
+// This accentuates the need for the creation of a real `window`.
+// e.g. var jQuery = require("jquery")(window);
+// See ticket trac-14549 for more info.
+var jQueryOrJQueryFactory = typeof window !== "undefined" && window.document ?
+	jQueryFactory( window, true ) :
+	function( w ) {
+		if ( !w.document ) {
+			throw new Error( "jQuery requires a window with a document" );
+		}
+		return jQueryFactory( w );
+	};
+
+function jQueryFactory( window, noGlobal ) {
+
+// @CODE
+// build.js inserts compiled jQuery here
+
+return jQuery;
+
+}
+
+export {
+	jQueryOrJQueryFactory as jQuery,
+	jQueryOrJQueryFactory as $
+};
+
+export default jQueryOrJQueryFactory;
diff --git a/src/wrapper.js b/src/wrapper.js
index 8a3dc53e0..fa8240e1e 100644
--- a/src/wrapper.js
+++ b/src/wrapper.js
@@ -42,4 +42,5 @@
 // build.js inserts compiled jQuery here
 
 return jQuery;
+
 } );