Add support for Heroku Stack-22.

README.md

@@ -16,6 +16,7 @@
 * Erlang - Prebuilt packages (17.5, 17.4, etc)
   * The full list of prebuilt packages can be found here: 
     * gigalixir-20 or heroku-20 stacks: https://repo.hex.pm/builds/otp/ubuntu-20.04/builds.txt
+    * heroku-22 stacks: https://repo.hex.pm/builds/otp/ubuntu-22.04/builds.txt
     * All other stacks: https://github.com/HashNuke/heroku-buildpack-elixir-otp-builds/blob/master/otp-versions
 * Elixir - Prebuilt releases (1.0.4, 1.0.3, etc) or prebuilt branches (master, v1.7, etc)
   * The full list of releases can be found here: https://github.com/elixir-lang/elixir/releases

lib/canonical_version.sh

@@ -1,11 +1,17 @@
 #!/usr/bin/env bash
 
 erlang_builds_url() {
-  if [ "$STACK" = "heroku-20" ]; then
-    erlang_builds_url="https://repo.hex.pm/builds/otp/ubuntu-20.04"
-  else
-    erlang_builds_url="https://s3.amazonaws.com/heroku-buildpack-elixir/erlang/cedar-14"
-  fi
+  case "${STACK}" in
+    "heroku-20")
+      erlang_builds_url="https://repo.hex.pm/builds/otp/ubuntu-20.04"
+      ;;
+    "heroku-22")
+      erlang_builds_url="https://repo.hex.pm/builds/otp/ubuntu-22.04"
+      ;;
+    *)
+      erlang_builds_url="https://s3.amazonaws.com/heroku-buildpack-elixir/erlang/cedar-14"
+      ;;
+  esac
   echo $erlang_builds_url
 }
 
@@ -15,13 +21,20 @@ fetch_elixir_versions() {
 }
 
 fetch_erlang_versions() {
-  if [ "$STACK" = "heroku-20" ]; then
-    url="https://repo.hex.pm/builds/otp/ubuntu-20.04/builds.txt"
-    curl -s "$url" | awk '/^OTP-([0-9.]+ )/ {print substr($1,5)}'
-  else
-    url="https://raw.githubusercontent.com/HashNuke/heroku-buildpack-elixir-otp-builds/master/otp-versions"
-    curl -s "$url"
-  fi
+  case "${STACK}" in
+    "heroku-20")
+      url="https://repo.hex.pm/builds/otp/ubuntu-20.04/builds.txt"
+      curl -s "$url" | awk '/^OTP-([0-9.]+ )/ {print substr($1,5)}'
+      ;;
+    "heroku-22")
+      url="https://repo.hex.pm/builds/otp/ubuntu-22.04/builds.txt"
+      curl -s "$url" | awk '/^OTP-([0-9.]+ )/ {print substr($1,5)}'
+      ;;
+    *)
+      url="https://raw.githubusercontent.com/HashNuke/heroku-buildpack-elixir-otp-builds/master/otp-versions"
+      curl -s "$url"
+      ;;
+  esac
 }
 
 exact_erlang_version_available() {