Add documentation for both environment variables

Author: marvin-bitterlich

src/doc/src/reference/environment-variables.md

@@ -184,6 +184,8 @@ let version = env!("CARGO_PKG_VERSION");
 * `CARGO_PKG_DESCRIPTION` — The description from the manifest of your package.
 * `CARGO_PKG_HOMEPAGE` — The home page from the manifest of your package.
 * `CARGO_PKG_REPOSITORY` — The repository from the manifest of your package.
+* `CARGO_CRATE_NAME` — The name of the crate that is currently being compiled.
+* `CARGO_BIN_NAME` — The name of the binary that is currently being compiled (if it is a binary).
 * `OUT_DIR` — If the package has a build script, this is set to the folder where the build
               script should place its output. See below for more information.
               (Only set during compilation.)