Merge #957: Documentation regarding absolute_fee and fee_rate updated

10b4b6c Documentations regarding absolute_fee and fee_rate updated (TATHAGATA ROY)

Pull request description:

  ### Description
  This pr solves this issue #856
  Updated the documentation for absolute fee and fee rate in BDK docs

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)

  #### Bugfixes:

  * [x] I'm linking the issue being fixed by this PR

ACKs for top commit:
  danielabrozzoni:
    ACK 10b4b6c

Tree-SHA512: 5b5f360b742313443368dc0b75275c38888cb358545661f7d9c78f3290789c50ffa9830e18473055d8e3da544c7d9527b023a1acdb28eaf862b24c892b23e9c4

Author: danielabrozzoni

crates/bdk/src/wallet/tx_builder.rs

@@ -190,6 +190,9 @@ impl<'a, D, Cs: CoinSelectionAlgorithm, Ctx: TxBuilderContext> TxBuilder<'a, D,
     }
 
     /// Set an absolute fee
+    /// The fee_absolute method refers to the absolute transaction fee in satoshis (sats).
+    /// If anyone sets both the fee_absolute method and the fee_rate method,
+    /// the fee_absolute value will take precedence over the fee_rate.
     pub fn fee_absolute(&mut self, fee_amount: u64) -> &mut Self {
         self.params.fee_policy = Some(FeePolicy::FeeAmount(fee_amount));
         self