Add Post-installation script for Cli.js deprecation and migration

[lmgyuan]

Add Post-installation script for Cli.js deprecation and migration

Per discussions about the #1226, we want to include a post-installation script to notify people that we are deprecating the cli.js in generator repository and offer them migration information.

The following is a proposed message logged after the installation. The migration url is a placeholder since we don't have a url yet. Happy to receive comments and discuss any ideas!

// postinstall.js
console.log(`
*************************************
*                                   *
*  DEPRECATION NOTICE               *
*                                   *
*************************************

The use of 'Cli.js' for documentation generation is deprecated and will be removed in future releases.

Please migrate to the new AsyncAPI CLI using the following guide:

1. Install AsyncAPI CLI:
   $ npm install -g @asyncapi/cli

2. Update your commands:
   Replace the deprecated 'Cli.js' commands with their AsyncAPI CLI equivalents.

Example Migration:

Before Migration (Using 'Cli.js'):
$ node Cli.js ./asyncapi.yaml ./template -o ./output -p param1=value1 --debug --install --disable-hook hookType=hookName

After Migration (Using AsyncAPI CLI):
$ asyncapi generate fromTemplate ./asyncapi.yaml ./template --output ./output --param param1=value1 --debug --install --disable-hook hookType=hookName

For more details, please visit: [Migration Guide URL]

Thank you for your understanding and cooperation.
`);