Add scripts and configuration for building snap package (#25064)

Release Notes:

- N/A

---------

Co-authored-by: Soumyadeep Ghosh <soumyadeepghosh2004@zohomail.in>

script/snap-try

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+
+# This script is intended to be run after `snap-build`.
+#
+# It expects a version to be passed as the first argument, and expects
+# the built `.snap` for that version to be in the current directory.
+#
+# This will uninstall the current `zed` snap, replacing it with a snap
+# that directly uses the `snap/unpacked` directory.
+
+set -euxo pipefail
+
+if [ "$#" -ne 1 ]; then
+  echo "Usage: $0 <release_version>"
+  exit 1
+fi
+
+# Rerun as root
+[ "$UID" -eq 0 ] || exec sudo bash -e "$0" "$@"
+
+snap remove zed || true
+mkdir -p snap
+rm -rf snap/unpacked
+unsquashfs -dest snap/unpacked "zed_$1_amd64.snap"
+snap try --classic snap/unpacked