Fix nrf monotonics (#852)

* Fix nrf::timer

* Bootstrap nrf52840-blinky example

* More work on nrf blinky example

* Fix README

* Add asserts for correct timer functionality

* Add correctness check to other monotonics as well

* Update Changelog

* Fix potential timing issues

* Fix race condition in nrf::rtc

* Add changelog

* Add rtc blinky example

* Change rtc example to RC lf clock source

* Add changelog to rtic-time

* Add changelog

* Attempt to fix CI

* Update teensy4-blinky Cargo.lock

examples/nrf52840_blinky/.cargo/config.toml

@@ -0,0 +1,18 @@
+[target.'cfg(all(target_arch = "arm", target_os = "none"))']
+runner = "probe-rs run --chip nRF52840_xxAA"
+
+rustflags = [
+  "-C", "linker=flip-link",
+  "-C", "link-arg=-Tlink.x",
+  "-C", "link-arg=-Tdefmt.x",
+  # This is needed if your flash or ram addresses are not aligned to 0x10000 in memory.x
+  # See https://github.com/rust-embedded/cortex-m-quickstart/pull/95
+  "-C", "link-arg=--nmagic",
+]
+
+[build]
+target = "thumbv7em-none-eabihf" # Cortex-M4F and Cortex-M7F (with FPU)
+
+[alias]
+rb = "run --bin"
+rrb = "run --release --bin"