renesas-ra/README.md: Add known issue about lightsleep and deepsleep.

TakeoTakahashi2020 · TakeoTakahashi2020 · commit 62db8e540b30 · 2022-03-29T20:17:26.000+09:00
Signed-off-by: Takeo Takahashi &lt;takeo.takahashi.xv@renesas.com&gt;
diff --git a/ports/renesas-ra/README.md b/ports/renesas-ra/README.md
@@ -63,6 +63,13 @@ Please refer to the `renesas-ra` quick reference.
 
 ## Known issues
 
+### all boards
+* machine.lightsleep(time_ms) and machine.deepsleep(time_ms) raise uncaught exceptions.
+
+    >>> machine.deepsleep(1000)
+    >>> Uncaught exception in ExtInt interrupt handler line 16
+    TypeError:
+
 ### RA4M1-CLICKER
 * mpremote: mount command is not available due to limited memory resources.
 
