Add RTIC example.

examples/nrf52840-rtic/.cargo/config.toml

@@ -0,0 +1,9 @@
+[target.'cfg(all(target_arch = "arm", target_os = "none"))']
+# replace nRF82840_xxAA with your chip as listed in `probe-rs-cli chip list`
+runner = "probe-rs-cli run --chip nRF52840_xxAA"
+
+[build]
+target = "thumbv7em-none-eabi"
+
+[env]
+DEFMT_LOG = "trace"