Adds using Swift from C++ example by jiawen · Pull Request #1454 · bazelbuild/rules_swift

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@jiawen

The following contributors were found for this pull request:

✅ 0d83110 Author: @jiawen <ji***n@mit.edu>
✅ d5face6 Author: @keith <kei******ley@gmail.com>

(Only the first commit for a unique contributor is listed.)