Fix npm publish warnings about the package.json format

This commit removes the following warning logs from the `npm publish`
output:

```
npm warn publish npm auto-corrected some errors in your package.json when publishing.  Please run "npm pkg fix" to address these errors.
npm warn publish errors corrected:
npm warn publish Removed invalid "scripts"
npm warn publish "repository.url" was normalized to "git+https://github.com/mozilla/pdfjs-dist.git"
```

For the "scripts" section it turns out that if the package doesn't have
any scripts it's expected to explicitly set it to an empty object; refer
to npm/cli#6918 and
denoland/dnt#414.

For the "repository.url" section it turns out that the URL must point to
a Git URL that doesn't resolve to an HTML page in the browser; refer to
https://docs.npmjs.com/cli/v10/configuring-npm/package-json#repository.

gulpfile.mjs

@@ -78,7 +78,7 @@ const COMMON_WEB_FILES = [
 ];
 const MOZCENTRAL_DIFF_FILE = "mozcentral.diff";
 
-const DIST_REPO_URL = "https://github.com/mozilla/pdfjs-dist";
+const DIST_REPO_URL = "https://github.com/mozilla/pdfjs-dist.git";
 
 const CONFIG_FILE = "pdfjs.config";
 const config = JSON.parse(fs.readFileSync(CONFIG_FILE).toString());
@@ -2231,6 +2231,7 @@ function packageJson() {
     engines: {
       node: ">=18",
     },
+    scripts: {},
   };
 
   return createStringSource(