Create a documentation about usage of configuration

[homura]

Most of the last parameters in the methods that concern building transactions using @ckb-lumos/common-script, such as common.prepareSigningEntries, common.transfer, common.injectCapacity, etc., are of type Option and contain an optional field named config. If developers do not provide a config, Lumos will use the config from config.initializeConfig in the first place, or if initializeConfig is not set either, it will use the mainnet config as the default