chore: exclude TS files from final tarball (#23)

Partially addresses #18

Verified that tarball (`dist/js/[email protected]`) doesn't include TS files anymore.

Author: Eugene Cheung

.npmignore

@@ -9,6 +9,7 @@ const project = new awscdk.AwsCdkConstructLibrary({
   author: "CDK Monitoring Constructs Team",
   authorAddress: "[email protected]",
   defaultReleaseBranch: "main",
+  stability: "experimental",
 
   cdkVersion: CDK_VERSION,
   cdkVersionPinning: true,
@@ -91,4 +92,9 @@ project.eslint.addRules({
   "prettier/prettier": "error",
 });
 
+// Don't need to include the TypeScript source files in the tarball; the transpiled JS files and
+// typing files are sufficient.
+project.addPackageIgnore("*.ts");
+project.addPackageIgnore("!*.d.ts");
+
 project.synth();