just: Add just fmt

We already have a `just` command to check the formatting, add one to run
the formatter. Use the more terse `just fmt` although the difference
from `just format` is not super obvious it is documented in the default
output of `just`.

justfile

@@ -13,6 +13,10 @@ check:
 lint:
   cargo +$(cat ./nightly-version) clippy --workspace --all-targets --all-features -- --deny warnings
 
+# Run cargo fmt
+fmt:
+  cargo +$(cat ./nightly-version) fmt --all
+
 # Check the formatting
 format:
   cargo +$(cat ./nightly-version) fmt --all --check