staking_actions: add additional docs

models/descriptions/staking_action.md

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+{% docs staking_action %}
+
+The staking action performed in this transaction. Can be `"Stake"` or `"Unstake"`.
+
+{% enddocs %}

models/descriptions/staking_pool_address.md

@@ -1,5 +1,5 @@
 {% docs staking_pool_address %}
 
-The address of the staking pool.
+The pool address delegated into.
 
 {% enddocs %}

models/descriptions/staking_stake_amount.md

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+{% docs staking_stake_amount %}
+
+The amount staked or delegated toward securing the NEAR network.
+
+{% enddocs %}