feat(vk-messenger): add VK Messenger package

Repacks the official Electron build vk.me/app serves directly (no GitHub
release or distro repo for this product). Upstream's own .deb installs
under the literal Cyrillic product name /opt/VK Мессенджер — package()
resolves that directory dynamically instead of hardcoding it, then lays
the payload out under a clean /opt/vk-messenger to match this repo's
convention.

vk-messenger/.stapler/update-check

@@ -0,0 +1,6 @@
+#!/bin/bash
+set -euo pipefail
+
+package_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+repo_root="$(cd "${package_dir}/.." && pwd)"
+exec "${repo_root}/tools/package_updates.sh" check "$(basename "$package_dir")"