#257: replace sync-request with curl

[nacNAC333]

Fixes #257

Replaces the sync-request npm package with curl via child_process.execSync for fetching Maven Central metadata.

sync-request pulls in a large transitive dependency tree and has known issues with newer Node versions. curl is universally available on all supported platforms (macOS, Linux, Windows via PowerShell).

Changes:

• Rewrite parser-version.js to use execSync("curl ...") instead of sync-request
• Remove sync-request from package.json dependencies
• Add exists() method for version validation using HTTP HEAD check

[yegor256]

@nacNAC333 Thanks for your contribution, we appreciate it! Before we can merge this pull request, we need to see all CI workflows pass without errors. We can't merge the pull request into the master branch unless all workflows are green. Try to fix them, also paying attention to code style issues.