jitsi-meet: add passthru.updateScript

Pull version number from stable releases, to ensure
that the latest stable release is used.

pkgs/servers/web-apps/jitsi-meet/default.nix

···
     single-host-smoke-test = nixosTests.jitsi-meet;
   };
 
+  passthru.updateScript = ./update.sh;
+
   meta = with lib; {
     description = "Secure, Simple and Scalable Video Conferences";
     longDescription = ''

pkgs/servers/web-apps/jitsi-meet/update.sh

···
+#!/usr/bin/env nix-shell
+#!nix-shell -i bash -p curl pup common-updater-scripts
+
+set -eu -o pipefail
+
+version="$(curl https://download.jitsi.org/stable/ | \
+    pup 'a[href] text{}' | \
+    awk -F'[_-]' '/jitsi-meet-web_/ {printf $4"\n"}' | \
+    sort -u | \
+    tail -n 1)"
+
+update-source-version jitsi-meet "$version"