add prdoc

Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>

prdoc/pr_5423.prdoc

@@ -0,0 +1,18 @@
+title: Runtime support for candidate receipt v2 (RFC103)
+
+doc:
+  - audience: [Runtime Dev, Node Dev]
+    description: |
+     Implementation of [RFC103](https://github.com/polkadot-fellows/RFCs/pull/103) in the relay chain runtime.
+     The runtime will accept and validate the new receipts only if the `FeatureIndex::CandidateReceiptV2` 
+     feature bit is enabled.
+
+crates:
+  - name: polkadot-primitives
+    bump: major
+  - name: polkadot-runtime-parachains
+    bump: patch
+  - name: rococo-runtime
+    bump: patch
+  - name: westend-runtime
+    bump: patch