- Add Basic Auth support for commonAPI

[Lizzy127]

• Add Basic Auth support for commonAPI
• Add Mainnet/Ropsten Chainstack endpoints
• Trim trailing whitespaces

Originally posted by @easeev in etherscan/ethvalidate#12

Originally posted by @Vovanchik25071982 in https://github.com/etherscan/ethvalidate/issues/83

Originally posted by @Vovanchik25071982 in https://github.com/etherscan/ethvalidate/issues/84