docs: release-notes: Add note on erase/write block size checking

Adds notes on these new features

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>

docs/release-notes.d/compatible-slots.md

@@ -0,0 +1,7 @@
+- Added optional write block size checking to ensure expected
+  sizes match what is available on the hardware.
+- Added optional erase size checking to ensure expected sizes
+  match what is available on the hardware.
+- Added debug logs for zephyr to output discrepencies in erase
+  and write block sizes in dts vs actual hardware configuration
+  at run-time.