Add yaml_elixir dependency to fix snmpkit compile warning

Resolves YamlElixir.read_from_file/1 undefined warning during compilation

mix.exs

@@ -58,6 +58,7 @@ defmodule Towerops.MixProject do
       {:swoosh, "~> 1.16"},
       {:req, "~> 0.5"},
       {:snmpkit, "~> 1.3"},
+      {:yaml_elixir, "~> 2.9"},
       {:telemetry_metrics, "~> 1.0"},
       {:telemetry_poller, "~> 1.0"},
       {:gettext, "~> 1.0"},