Add to RELEASE.md the informations about resize and widevine

RELEASE.md

@@ -13,3 +13,23 @@ Image variants:
 This is development system, not ready for production usage,
 and build in insecure configuration. This does not support secure
 boot, nor it does not perform rootfs verification ubon boot.
+
+### 1. Resize STATE
+
+After installing Chromium OS you should resize STATE partition:
+
+1. Press: `Ctrl+Alt+F2`,
+2. Login: `chronos/chronos`,
+3. Run: `sudo rockpro64-resize-statefs.sh`, enter password `chronos`,
+4. Exit and go back to the Chromium OS with `Ctrl+Alt+F1`.
+
+### 2. Install Widevine DRM
+
+The build supports Widevine DRM, but does not ship the binary
+as this is against Google license. You can install it manually,
+but first follow the resize manual:
+
+1. Press: `Ctrl+Alt+F2`,
+2. Login: `chronos/chronos`,
+3. Run: `sudo rockpro64-install-widevine.sh`,
+4. Reboot: `sudo reboot`.