Add the concept of local tasks with an example

examples/embassy-stm32g4/src/bin/spawn_local.rs

@@ -0,0 +1,42 @@
+#![no_main]
+#![no_std]
+
+use core::marker::PhantomData;
+use rtic::app;
+use {defmt_rtt as _, panic_probe as _};
+pub mod pac {
+    pub use embassy_stm32::pac::Interrupt as interrupt;
+    pub use embassy_stm32::pac::*;
+}
+
+#[app(device = pac, peripherals = false, dispatchers = [SPI1])]
+mod app {
+    use super::*;
+
+    #[shared]
+    struct Shared {}
+
+    #[local]
+    struct Local {}
+
+    #[init]
+    fn init(_cx: init::Context) -> (Shared, Local) {
+        task1::spawn().ok();
+        //task2::spawn(Default::default()).ok(); <--- This is rejected since it is a local task
+        (Shared {}, Local {})
+    }
+
+    #[task(priority = 1)]
+    async fn task1(cx: task1::Context) {
+        defmt::info!("Hello from task1!");
+        cx.local_spawner.task2(Default::default()).ok();
+    }
+
+    #[task(priority = 1, is_local_task = true)]
+    async fn task2(_cx: task2::Context, _nsns: super::NotSendNotSync) {
+        defmt::info!("Hello from task1!");
+    }
+}
+
+#[derive(Default)]
+struct NotSendNotSync(PhantomData<*mut u8>);