chore: @aws-cdk/toolkit-lib is now a part of the toolkit packages (#380)

Until we sort out #364 properly,
lets at least do this so that toolkit changes trigger a CLI release.

---
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under the terms of the Apache-2.0 license

Author: iliapolo

.projenrc.ts

@@ -174,6 +174,7 @@ function transitiveToolkitPackages(thisPkg: string) {
     '@aws-cdk/tmp-toolkit-helpers',
     '@aws-cdk/cloud-assembly-schema',
     '@aws-cdk/cloudformation-diff',
+    '@aws-cdk/toolkit-lib',
   ];
 
   return transitiveFeaturesAndFixes(thisPkg, toolkitPackages.filter(name => name !== thisPkg));