build(justfile): add format support (#66)

Allows for formatting of source code when running just all

Using the [fmt naming from Just's own](https://github.com/casey/just/blob/d15dad66c9d1cd342b99d0de2d2e99a610ee2fd8/justfile#L39)

Author: pratikpc

justfile

@@ -3,10 +3,15 @@ _default:
 
 # run doc, clippy, and test recipies
 all *args:
+  just fmt {{args}}
   just doc {{args}}
   just clippy {{args}}
   just test {{args}}
 
+# Format all code
+fmt *args:
+  cargo fmt --all {{args}}
+
 # run tests on all feature combinations
 test *args:
   cargo hack test --feature-powerset {{args}}