librunner 0.4.0

Rust library to assist runners on planning their workouts, races, and improve their health.
Documentation
# How To Contribute

## Publishing a New Version

1. Run all tests to make sure everything is still working as expected:

       $ cargo test

2. Generate the documentation at `target/doc/librunner` to check if it was properly updated with the latest changes:

       $ cargo doc

2. Increment the version number in the file `Cargo.toml`:

       version = "0.3.0" -> version = "0.4.0"

2. Commit the file `Cargo.toml` and push to the repository:

       $ git add Cargo.toml
       $ git commit -m "Incremented version number"
       $ git push origin main

3. Check if everything is ready to publish the library:

       $ cargo publish --dry-run

4. Finally, publish the library:

       $ cargo publish