Include Cargo.lock for reproducible builds

This project provides a library and an executable. Including a Cargo.lock allows
the executable to be built reliably (and is expected by third-parties, like
Nixpkgs). Those depending on the library are unaffected, since the Cargo.lock
files from dependencies will be ignored.

Author: Warbo

.gitignore

@@ -1,3 +1,2 @@
 target
-Cargo.lock
-*.bk
+*.bk