docs: update README with 32-bit build instructions

Added build instructions for 32-bit devices.

Author: traitimtrongvag

README.md

@@ -3,4 +3,10 @@ This is an experimental demo and may not function correctly in all scenarios.
 To build, run:
 ```bash
 cargo build --release --target aarch64-linux-android
-```
+```
+
+or for `32-bit` devices
+
+```bash
+cargo build --release --target armv7-linux-androideabi
+```