[meta] Remove non-essential files from npm package

~3x reduction in package size. ~5x reduction in on-disk size

https://docs.npmjs.com/cli/v11/configuring-npm/package-json#files

Reverts f81ece6
Removes:

* .github/
* example/
* test/
* .eslintrc
* .nycrc
* CHANGELOG.md

```
npm pack --dry-run
```

**Before**

```
=== Tarball Details ===
package size:  16.6 kB
unpacked size: 59.0 kB
total files:   26
```

**After**

```
=== Tarball Contents ===
1.1kB LICENSE
3.8kB README.md
6.3kB index.js
1.6kB package.json
=== Tarball Details ===
package size:  4.9 kB
unpacked size: 12.9 kB
total files:   4
```

Author: david-allison

package.json

@@ -4,7 +4,6 @@
 	"description": "parse argument options",
 	"main": "index.js",
 	"scripts": {
-		"prepack": "npmignore --auto --commentLines=auto",
 		"prepublishOnly": "safe-publish-latest",
 		"prepublish": "not-in-publish || npm run prepublishOnly",
 		"lint": "eslint --ext=js,mjs .",
@@ -15,6 +14,9 @@
 		"version": "auto-changelog && git add CHANGELOG.md",
 		"postversion": "auto-changelog && git add CHANGELOG.md && git commit --no-edit --amend && git tag -f \"v$(node -e \"console.log(require('./package.json').version)\")\""
 	},
+	"files": [
+		"index.js"
+	],
 	"testling": {
 		"files": "test/*.js"
 	},
@@ -44,7 +46,6 @@
 		"encoding": "^0.1.13",
 		"eslint": "=8.8.0",
 		"in-publish": "^2.0.1",
-		"npmignore": "^0.3.1",
 		"nyc": "^10.3.2",
 		"safe-publish-latest": "^2.0.0",
 		"tape": "^5.9.0"
@@ -59,10 +60,5 @@
 		"commitLimit": false,
 		"backfillLimit": false,
 		"hideCredit": true
-	},
-	"publishConfig": {
-		"ignore": [
-			".github/workflows"
-		]
 	}
 }