Fix icon path in README
The data/ directory was moved to app/data/.
Refs
# scrcpy (v1.23)
-<img src="data/icon.svg" width="128" height="128" alt="scrcpy" align="right" />
+<img src="app/data/icon.svg" width="128" height="128" alt="scrcpy" align="right" />
_pronounced "**scr**een **c**o**py**"_
