incus: add livecheck

By default, livecheck isn't able to check the `stable` URL for
`incus`, so it falls back to checking the Git tags from the `head`
URL. This adds a `livecheck` block that checks the first-party
download page, which links to the `stable` tarball.

Author: samford

Formula/i/incus.rb

@@ -6,6 +6,11 @@ class Incus < Formula
   license "Apache-2.0"
   head "https://github.com/lxc/incus.git", branch: "main"
 
+  livecheck do
+    url "https://linuxcontainers.org/incus/downloads/"
+    regex(/href=.*?incus[._-]v?(\d+(?:\.\d+)+)\.t/i)
+  end
+
   bottle do
     sha256 cellar: :any_skip_relocation, arm64_sequoia: "44913f8cad662c918fdfd54f5918cd957cc802d7d688b1354731a51a4d724f4a"
     sha256 cellar: :any_skip_relocation, arm64_sonoma:  "44913f8cad662c918fdfd54f5918cd957cc802d7d688b1354731a51a4d724f4a"