[Feature Request] Provide packaged .crx and .xpi assets in GitHub Releases

### Issue Details

Currently, GitHub releases only provide unpacked .zip archives. While this is fine for developer inspection, it creates substantial friction for ordinary users trying to install and update the extension across two increasingly prevalent scenarios:

Chromium MV2 Forks (Supermium, Helium, etc.)

The Chrome Web Store has completely deprecated and removed Manifest V2 extensions.

Users who continue relying on MV2 are migrating to community Chromium forks committed to preserving MV2 support (e.g., Supermium, Helium).

Installing an unpacked extension from a .zip forces browsers into Developer Mode, prompting persistent "Disable developer mode extensions" warnings on launch, and turns every minor update into an inconvenient manual folder replacement. A standalone .crx allows clean, persistent installation.

AMO Geo-blocking in Mainland China

Mozilla's Add-ons site (AMO) enforces regional restrictions that block users with mainland China IPs from accessing ad-blocker store pages, making standard web-store installation and automatic updates impossible.

Providing standalone .xpi packages on GitHub releases offers an essential alternative distribution channel, allowing Firefox users in restricted regions to install AdGuard directly without relying on third-party mirrors or complex network proxy setups.

### Proposed solution

Please update the release pipeline to build and attach pre-packaged .crx (for Chromium) and signed .xpi (for Firefox) binaries alongside the existing .zip archives on every GitHub release.

### Additional Information

uBlock Origin has offered direct .crx and .xpi assets in their GitHub releases for years, which has proven vital for users on alternative browser forks and in regions affected by store geofencing.