add basic codesandbox support

.codesandbox/Dockerfile

@@ -0,0 +1,4 @@
+# CodeSandbox supports debian & ubuntu based images
+FROM elixir:1.14
+
+RUN mix local.hex --force && mix local.rebar --force

.codesandbox/tasks.json

@@ -0,0 +1,18 @@
+{
+  // These tasks will run in order when initializing your CodeSandbox project.
+  "setupTasks": [
+    {
+      "name": "Get Dependencies",
+      "command": "mix deps.get"
+    }
+  ],
+
+  // These tasks can be run from CodeSandbox. Running one will open a log in the app.
+  "tasks": {
+    "test": {
+      "name": "Run Tests",
+      "command": "mix test",
+      "runAtStart": true
+    }
+  }
+}

README.md

@@ -52,7 +52,7 @@ any reasons why things _shouldn't_ work as expected on other operating systems,
 
 ```elixir
 Sketch.new()
-|> Sketch.set_fill({100, 100, 100})
+|> Sketch.fill({100, 100, 100})
 |> Sketch.square(%{origin: {0, 0}, size: 50})
 |> Sketch.run()
 ```