Improve dev tooling (#30)

* added ex_check and got it passing

* Set up ex_check to run in test env

* Added static code analysis

* Updated actions file

* Updated dockerfile

mix.exs

@@ -9,7 +9,11 @@ defmodule Pinchflat.MixProject do
       elixirc_paths: elixirc_paths(Mix.env()),
       start_permanent: Mix.env() == :prod,
       aliases: aliases(),
-      deps: deps()
+      deps: deps(),
+      preferred_cli_env: [
+        check: :test,
+        credo: :test
+      ]
     ]
   end
 
@@ -55,7 +59,9 @@ defmodule Pinchflat.MixProject do
       {:nimble_parsec, "~> 1.4"},
       {:mox, "~> 1.0", only: :test},
       {:credo, "~> 1.7", only: [:dev, :test], runtime: false},
-      {:faker, "~> 0.17", only: :test}
+      {:ex_check, "~> 0.14.0", only: [:dev, :test], runtime: false},
+      {:faker, "~> 0.17", only: :test},
+      {:sobelow, "~> 0.13", only: [:dev, :test], runtime: false}
     ]
   end