add link to qemu-run code; note that won't be published
*Printers* are *host* programs that receive log data, format it and display it.
The following printers are currently available:
-- `qemu-run`, parses data sent by QEMU over semihosting (ARM Cortex-M only)
+- [`qemu-run`], parses data sent by QEMU over semihosting (ARM Cortex-M only). NOTE: used for internal testing; won't be published to crates.io
- [`probe-run`], parses data sent over RTT (ARM Cortex-M only). NOTE: make sure you install the tool from git (not crates.io) and enable the "defmt" Cargo feature.
+[`qemu-run`]: https://github.com/knurling-rs/defmt/tree/main/qemu-run
[`probe-run`]: https://github.com/knurling-rs/probe-run
