feat: initialize Kurdistan SDK - independent fork of Polkadot SDK

pezkuwi/roadmap/implementers-guide/src/runtime-api/persisted-validation-data.md

@@ -0,0 +1,13 @@
+# Persisted Validation Data
+
+Yields the [`PersistedValidationData`](../types/candidate.md#persistedvalidationdata) for the given
+[`ParaId`](../types/candidate.md#paraid) along with an assumption that should be used if the para currently occupies a
+core:
+
+```rust
+/// Returns the persisted validation data for the given para and occupied core assumption.
+///
+/// Returns `None` if either the para is not registered or the assumption is `Freed`
+/// and the para already occupies a core.
+fn persisted_validation_data(at: Block, ParaId, OccupiedCoreAssumption) -> Option<PersistedValidationData>;
+```