(bashrc/navigate) added checks and aliases for pushd/popd if navigate does not exist

scripts/navigate_bash_setup.sh

@@ -1,5 +1,10 @@
 #!/usr/bin/env bash
 
+if ! $(which navigate &>/dev/null); then
+    printf "\033[0;31mcould not find 'navigate' on path" >&2
+    return 1
+fi
+
 function __call_navigate {
     arg_pid=" --pid $$ "
     eval "$(navigate ${arg_pid} $@)"