docs: add tutorial consumptional fee (#59)

* feat: load specific line of code from github

* docs: add tutorial consumptional fee

* fix: linter errors

* fix: linter errors

* fix: linter errors

* fix: remove github selected code

* fix: linter errors

* fix: add callout information

* fix: daily limit description

content/tutorials/consumptional-fee.md

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+---
+title: How to Enable Consumptional Fee?
+weight: 10
+---
+
+## Preface
+
+The blockchain ecosystem is continuously evolving, with new models and protocols emerging to address specific needs
+and challenges. One of these is [PIP-31](https://pips.pactus.org/PIPs/pip-31), the "Consumptional Fee Model," a
+unique approach to transaction fees within the Pactus blockchain network.
+Traditional fee models often impose fixed charges, potentially excluding lower-priority or low-fee transactions from
+timely processing. This can create barriers for users who prefer economical transactions over speed, particularly
+within decentralized environments where inclusion is a priority.
+
+This tutorial explores the foundation of the Consumptional Fee Model, designed to provide a balanced and flexible
+fee structure based on data consumption. This model allows users to benefit from a zero or low-fee option, albeit
+with trade-offs in transaction confirmation speed.
+The approach aims to incentivize efficient data usage while giving validators the flexibility to configure fees
+dynamically based on network demands and user transaction patterns.
+
+## Configuring the Consumptional Fee
+
+By default, the consumptional fee is disabled in the [configuration](https://github.com/pactus-project/pactus/blob/main/config/example_config.toml).
+
+```toml
+  # `tx_pool.fee` contains configuration to calculate the transaction fee.
+  [tx_pool.fee]
+
+    # The `fixed_fee` is a constant fee applied to each transaction, regardless of its size or type.
+    # Default is `0.01` PAC.
+    fixed_fee = 0.01
+
+    # The `daily_limit` is the number of bytes an account can send each day without paying a fee.
+    # The `daily_limit` is part of the consumptional fee model.
+    # To understand how the consumptional fee model works, you can refer to
+    # PIP-31: Consumptional Fee Mode (https://pips.pactus.org/PIPs/pip-31)
+    # Default is `360` bytes.
+    daily_limit = 360
+
+    # The `unit_price` defines the fee per byte in PAC.
+    # The `unit_price` is part of the consumptional fee model.
+    # If it is zero, the consumptional fee will be ignored.
+    # To understand how the consumptional fee model works, you can refer to
+    # PIP-31: Consumptional Fee Mode (https://pips.pactus.org/PIPs/pip-31)
+    # Default is `0.0` PAC.
+    unit_price = 0.0
+```
+
+{{< callout type="info" >}}
+When the consumptional fee model is enabled, each signer can have **1~2 zero-fee** transactions per day.
+{{< /callout >}}
+
+This configuration is recommended for enabling the consumptional fee, though you can adjust
+`daily_limit` and `unit_price` as needed.
+
+- `daily_limit` = the daily limit is the number of bytes an account can send each day without paying a fee.
+- `unit_price` = the fee per byte of data
+
+```toml
+  [tx_pool.fee]
+    fixed_fee = 0.0
+    daily_limit = 360
+    unit_price = 0.000005
+```
+
+After updating your node configuration, you will need to restart your node to enable the consumptional fee.