chore: Add GitHub workflows to exercise mage.

.github/workflows/api.yaml

@@ -0,0 +1,19 @@
+name: api
+
+on:
+  pull_request:
+  push:
+
+jobs:
+  mage:
+    runs-on: ubuntu-latest
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v4
+      -
+        name: Run Mage
+        uses: magefile/mage-action@v3
+        with:
+          version: latest
+          args: test

.github/workflows/git.yaml

@@ -0,0 +1,19 @@
+name: api
+
+on:
+  pull_request:
+  push:
+
+jobs:
+  mage:
+    runs-on: ubuntu-latest
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v4
+      -
+        name: Run Mage
+        uses: magefile/mage-action@v3
+        with:
+          version: latest
+          args: build test

.github/workflows/tmux-vcs-sync.yaml

@@ -0,0 +1,19 @@
+name: api
+
+on:
+  pull_request:
+  push:
+
+jobs:
+  mage:
+    runs-on: ubuntu-latest
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v4
+      -
+        name: Run Mage
+        uses: magefile/mage-action@v3
+        with:
+          version: latest
+          args: build test

api/magefiles/magefile.go

@@ -0,0 +1,14 @@
+//go:build mage
+// +build mage
+
+package main
+
+import (
+	"github.com/magefile/mage/sh"
+)
+
+var Default = Test
+
+func Test() error {
+	return sh.Run("go", "test", "./...")
+}