Add comment about keeping dependencies

src/dev/check.rs

@@ -7,6 +7,7 @@ use crate::{info_file::InfoFile, init::cargo_toml};
 pub fn check(info_file: InfoFile) -> Result<()> {
     // TODO: Add checks
 
+    // TODO: Keep dependencies!
     fs::write("Cargo.toml", cargo_toml(&info_file.exercises))
         .context("Failed to update the file `Cargo.toml`")?;
     println!("Updated `Cargo.toml`");