improvement: bring code up to date and add linters, etc.

.check.exs

@@ -0,0 +1,33 @@
+[
+  ## don't run tools concurrently
+  # parallel: false,
+
+  ## don't print info about skipped tools
+  skipped: false,
+
+  ## always run tools in fix mode (put it in ~/.check.exs locally, not in project config)
+  # fix: true,
+
+  ## don't retry automatically even if last run resulted in failures
+  # retry: false,
+
+  ## list of tools (see `mix check` docs for a list of default curated tools)
+  tools: [
+    ## curated tools may be disabled (e.g. the check for compilation warnings)
+    # {:compiler, false},
+
+    ## ...or have command & args adjusted (e.g. enable skip comments for sobelow)
+    {:sobelow, false},
+
+    ## ...or reordered (e.g. to see output from dialyzer before others)
+    # {:dialyzer, order: -1},
+
+    ## ...or reconfigured (e.g. disable parallel execution of ex_unit in umbrella)
+    # {:ex_unit, umbrella: [parallel: false]},
+
+    ## custom new tools may be added (Mix tasks or arbitrary commands)
+    # {:my_task, "mix my_task", env: %{"MIX_ENV" => "prod"}},
+    # {:my_tool, ["my_tool", "arg with spaces"]}
+    # {:esbuild, "mix esbuild prod"}
+  ]
+]