Do not publish `node_modules`

[moltar]

It appears that your node_modules directory is also published in the release tarball.

https://github.com/cuperman/cdk-appconfig/releases/download/v1.0.0/cdk-appconfig@1.0.0.jsii.tgz

## --- a list of all entries in the `package` dir.
$> ls
README.md      dist           jest.config.js node_modules   package.json   test           tsconfig.json

## --- total size
$> du -hs .
121M	.
121M	total

## --- remove node_modules
$> rm -rf node_modules

## --- new total size
$> du -hs .
1.4M	.