Added Rust crates script

Necessary to implement the installation of Rust and associated crates
which can be used by downstream configurations. This functionality was
originally part of the macOS Configuration project but has been moved
here to provide a common foundation in which to build upon.

lib/installers.sh

@@ -171,6 +171,15 @@ install_program() {
 }
 export -f install_program
 
+# Installs Rust.
+# Parameters: None.
+install_rust() {
+  if ! command -v cargo > /dev/null; then
+    curl --proto "=https" --tlsv1.2 --fail --silent --show-error https://sh.rustup.rs | sh
+  fi
+}
+export -f install_rust
+
 # Installs an application via a tar file.
 # Parameters: $1 (required) - URL, $2 (required) - Application name, $3 (required) - Decompress options.
 install_tar_app() {