Add example for custom error handler

Makefile

diff --git a/Makefile b/Makefile
index d912813..34d223e 100644
--- a/Makefile
+++ b/Makefile
@@ -43,6 +43,7 @@
 	PLATFORM=nrf52 cargo build --release --target=thumbv7em-none-eabi --examples
 	PLATFORM=nrf52 cargo build --release --target=thumbv7em-none-eabi --examples --features=alloc
 	PLATFORM=opentitan cargo build --release --target=riscv32imc-unknown-none-elf --examples
+	cd core && cargo build --release --target=thumbv7em-none-eabi --examples --features=custom_panic_handler && cd ..
 
 .PHONY: test
 test:

core/Cargo.toml

diff --git a/core/Cargo.toml b/core/Cargo.toml
index 64fa96e..f0477eb 100644
--- a/core/Cargo.toml
+++ b/core/Cargo.toml
@@ -11,3 +11,8 @@
 
 [dependencies]
 linked_list_allocator = { optional = true, version = "=0.6.5", default-features = false }
+
+[[example]]
+name = "custom_panic"
+path = "examples/custom_handler.rs"
+required-features = ["custom_panic_handler"]
\ No newline at end of file

core/examples/custom_handler.rs

diff --git a/core/examples/custom_handler.rs b/core/examples/custom_handler.rs
new file mode 100644
index 0000000..8cccca9
--- /dev/null
+++ b/core/examples/custom_handler.rs
@@ -0,0 +1,12 @@
+#![no_std]
+
+use libtock_core::result::CommandError;
+
+fn main() -> Result<(), CommandError> {
+    panic!("Bye world!");
+}
+
+#[panic_handler]
+unsafe fn panic_handler(_info: &core::panic::PanicInfo) -> ! {
+    loop {}
+}