docs: make readme more precise (#84)

There is also a file in the repository called `bazelrc-preset.bzl`. The
text can also be understood to append the content of the file to your
own `MODULE.bazel`.

Especially new users may be a little less confused when it is stated
explicitly using an example.

---------

Co-authored-by: Markus Hofbauer <[email protected]>

Author: adrianimboden

README.md

@@ -21,6 +21,10 @@ Read [the Bazel bazelrc documentation](https://bazel.build/run/bazelrc).
 ## Install
 
 1. Add `bazelrc-preset.bzl` to your `MODULE.bazel` file.
+    ```starlark
+    bazel_dep(name = "bazelrc-preset.bzl", version = "...")
+    ```
+    
 2. Call it from a `BUILD` file, for example in `tools/BUILD`:
 
     ```starlark