Add blink PWM example

gpio/gpio_blink_pwm/application.fam

@@ -0,0 +1,10 @@
+App(
+    appid="gpio_blink_pwm",
+    name="GPIO Blink PWM",
+    apptype=FlipperAppType.EXTERNAL,
+    entry_point="gpio_blink_pwm_app",
+    requires=["gui"],
+    stack_size=2 * 1024,
+    fap_icon="blink_pwm.png",
+    fap_category="GPIO",
+)