fix: add the entry file

src/main.ts

@@ -0,0 +1,23 @@
+import * as core from "@actions/core"
+
+export async function main(): Promise<number> {
+  try {
+    // TODO
+  } catch (err) {
+    core.error(err as string | Error)
+    core.setFailed("install-cpp failed")
+    return 1
+  }
+
+  core.info("install-cpp succeeded")
+  return 0
+}
+
+main()
+  .then((ret) => {
+    process.exitCode = ret
+  })
+  .catch((error) => {
+    core.error("main() failed!", error)
+    process.exitCode = 1
+  })