fix(examples) fix MicroPython examples and run the examples with CI (#2339)

* Fixes to micropython examples

Added missing images and fonts under 'assets'. Since .bin is in gitignore, renamed fonts to .fnt

* Update build_micropython workflow

Build the unix port dev variant and run tests.

See: https://github.com/lvgl/lv_binding_micropython/issues/151

.github/workflows/build_micropython.yml

@@ -33,11 +33,6 @@ jobs:
     - name: Build mpy-cross
       run: make -j $(nproc) -C mpy-cross
     - name: Build the unix port
-      run: make -j $(nproc) -C ports/unix
-    - name: Run advanced_demo
-      run: >
-        echo "import gc,utime;
-        utime.sleep(5);
-        gc.collect();
-        utime.sleep(5)" |
-        ports/unix/micropython -i lib/lv_bindings/examples/advanced_demo.py
+      run: make -j $(nproc) -C ports/unix VARIANT=dev DEBUG=1
+    - name: Run tests      
+      run: lib/lv_bindings/tests/run.sh