Add description for custom fields in history ledgers table (#57)

* Add description for custom fields in history ledgers table

* Add description for soroban_fee_write_1kb

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Co-authored-by: Amisha Singla <[email protected]>

models/docs/sources/history_ledgers.md

@@ -108,3 +108,15 @@ The number of failed transactions submitted to the network in this ledger. The t
 {% docs tx_set_operation_count %}
 The total number of operations in the transaction set for this ledger, including failed transactions.
 {% enddocs %}
+
+{% docs soroban_fee_write_1kb %}
+The write fee is dynamic fee that grows linearly with the size of the ledger. The write fee for a given ledger is recorded in the ledger header and has a direct relationship to the bucketlist size of the ledger db.
+{% enddocs %}
+
+{% docs node_id %}
+The id of winning validator node which is allowed to write transaction set to the network. The winning validator is decided by the network.
+{% enddocs %}
+
+{% docs signature %}
+The signing hash of the validator node which writes the transaction set to the network.
+{% enddocs %}