feat: add virtual contract note API

[ranjanrak]

• get_virtual_contract_note: Addition of virtual contract note charges API.
• test_virtual_contract_note: Addition of unit tests for VCN API.
• Update the mock_response submodule for new tests.
• Addition of examples for get_virtual_contract_note method in the examples folder.
• Remove py 2.7 from setup.py and github workflow as it's no more supported.
• Remove pypy2, and pypy3 from GitHub workflow as cryptography > 40 requires pypy > 7.3.10
• Update readme with the breaking changes of Drop Support for Python 2.7
• Update version with major release version 5.0.0-beta