Adopt code for Khalani Protocol

[serejke]

This PR contains the patches on top of the origin Avalanche Faucet that adopt for Khalani protocol:

• allow to configure faucet from a file specified by CONFIG_FILE
• allow to override RPC URLs with ENV variables of name EVM_CHAINS_${ID}_RPC, where ID is the chain ID specified in evmchains of config.json, for example EVM_CHAINS_KHALANITESTNET_RPC
• allow to disable captcha verification — needed to test the deployment and then register Google Captcha for the production domain
• added Khalani Protocol branding (logo / docs)
• GitHub pipeline to build a Docker image

[serejke]

Sorry, the wrong repo... I intended to open PR against our fork