added instructions to enter bootloader

keyboards/handwired/wakizashi40/readme.md

@@ -13,3 +13,7 @@ Make example for this keyboard (after setting up your build environment):
     qmk compile -kb handwired/wakizashi40 -km via
 
 See [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) then the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information.
+
+## Bootloader
+
+* **Keycode in layout**: Press the key mapped to `RESET` if it is available (Capslock + R).