Fixes, code enhancements
* remove lowercase call while parsing csv for adding users
* set user agent (#219)
* Add and clean up logging, always include version in logs (#234, #224)
* Encoding filter values to handle spaces and special chars in filters  (#225)
* replace polling code with library call
* readme updates (#235)
* Read and warn when user sets thumbnail options. (including 'not yet implemented' message for --thumbnail-group)
* freeze tsc dependency (#248)

New functionality
* added new --filter option to pass in un-encoded value for simpler input
* Add --url, --include-all/--embedded-datasources for create/refresh/delete extract commands (#227)
* Add new command for listing content on the site (#230)
* Implement publishing options overwrite/append/replace arguments (including not-yet-implemented message for --replace) (#236)
* implement --proxy, --no-proxy,  --use-certificate option  (#241)
* add --token-file option (#243)

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Co-authored-by: Bhuvnesh Singh <bhuvnesh.singh@salesforce.com>