chore(publish): exclude all test files from npm package

Update the files exclusion pattern from `!example/*.test.ts` to
`!**/*.test.ts` to exclude all test files in src/ directory from
being published to npm. Previously only example test files were
excluded, leaving 12 test files in src/ included in the package.

Author: ryoppippi

package.json

@@ -28,7 +28,7 @@
 	"module": "./dist/index.mjs",
 	"types": "./dist/index.d.mts",
 	"files": [
-		"!example/*.test.ts",
+		"!**/*.test.ts",
 		"LICENSE",
 		"README.md",
 		"dist",