[meta] use npmignore to autogenerate an npmignore file

Author: ljharb

.gitignore

@@ -23,3 +23,5 @@ package-lock.json
 
 coverage/
 .nyc_output/
+
+.npmignore

.npmignore

@@ -9,6 +9,7 @@
 	"license": "MIT",
 	"main": "index.js",
 	"scripts": {
+		"prepack": "npmignore --auto --commentLines=autogenerated",
 		"prepublishOnly": "safe-publish-latest",
 		"prepublish": "not-in-publish || npm run prepublishOnly",
 		"pretest": "npm run lint",
@@ -51,6 +52,7 @@
 		"eslint": "=8.8.0",
 		"for-each": "^0.3.3",
 		"in-publish": "^2.0.1",
+		"npmignore": "^0.3.0",
 		"nyc": "^10.3.2",
 		"safe-publish-latest": "^2.0.0",
 		"tape": "^5.6.1"
@@ -83,5 +85,11 @@
 		"commitLimit": false,
 		"backfillLimit": false,
 		"hideCredit": true
+	},
+	"publishConfig": {
+		"ignore": [
+			".github/workflows",
+			"test-corejs.js"
+		]
 	}
 }