Add relayer fee configuration to relayer

[salman01zp]

Summary of changes

• [x] Add Relayer fee configuration
• [x] Update test
• [x] Update config files
• [x] Update readme

Added Relayer fee configuration, which can be used by each chain to configure relayer_profit_percent and max_refund_amount of the relayer

/// Transaction relayer fee configuration.
#[derive(Debug, Clone, Deserialize, Serialize)]
#[serde(rename_all(serialize = "camelCase", deserialize = "kebab-case"))]
pub struct RelayerFeeConfig {
    /// Relayer profit percent per transaction fee for relaying
    pub relayer_profit_percent: f64,
    /// Maximum refund amount per transaction relaying
    pub max_refund_amount: f64,
}

impl Default for RelayerFeeConfig {
    fn default() -> Self {
        Self {
            relayer_profit_percent: 5.,
            max_refund_amount: 5.,
        }
    }
}

Reference issue to close (if applicable)

• Closes #570

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Code Checklist

• [ ] Tested
• [ ] Documented

[shekohex]

@salman01zp any idea why the CI is failing?

[salman01zp]

hmm, some issue with the tangle node. https://github.com/webb-tools/relayer/actions/runs/5798481431/job/15719574758#step:10:66