Bump version

Changes:

* UART support added.
* SPI reimplemented for embedded-hal 1.0.
* Adjust to RIOT API changes in gcoap, GPIO, shell XFA.
* Error enhancements (niche used, Display and Error added, pretty if
  tiny_strerror is available).
* GNRC enhancements (simplifications, debug, added methods).
* Added contributing guide.
* Documentation fixes.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "riot-wrappers"
-version = "0.9.1"
+version = "0.9.2"
 authors = ["Christian Amsüss <[email protected]>"]
 edition = "2021"
 rust-version = "1.79.0"