Feature request: Detailed validation documentation

[imWildCat]

Is your feature request related to a problem? Please describe.
A number of users are concerned about the validation rules for proxies. More detailed doc is needed.

Describe the solution you'd like

• Implement a better algorithm to validate the IPs
  • HTTPS proxy validation
  • Create a ValidationTask class as a wrapper of ProxyIP for the validation queue in order to:
    • Retry if the initial validation fails
  • English and Chinese doc about this validation algorithm

Describe alternatives you've considered
None.

Additional context
None