Update CONTRIBUTING.md

Author: o2sh

Diff for: CONTRIBUTING.md

@@ -113,9 +113,9 @@ To add a new package manager, make sure to follow these steps:
 
 **Example**:
 
-`{ Cargo, "cargo", "Cargo.toml", cargo },`
+`{ Cargo, "cargo", [ ("Cargo.toml", cargo) ] },`
 
-The first item `Cargo` corresponds to the name of the package manager. The second item `cargo` is the display name. Then we have the name of the package manager file that will be parsed: `Cargo.toml`. The last item `cargo` corresponds to the function mame responsible for parsing the package manager file, cf. step 2.
+The first item `Cargo` corresponds to the name of the package manager. The second item `cargo` is the display name. Then we have the name of the package manager file that will be parsed: `Cargo.toml` along with its parser `cargo` (cf. step 2), notice that the third item is an array of tuple in case the package manager has multiple parsers (e.g. pip).
 
 2. in `src/onefetch/deps/package_parser.rs`: create a function that takes an input of type `&str` representing the content of the package manager's file, and returns a `usize` as its number of dependencies.