Add a config file checking based on enviroment variable file PATH

[gbgabo]

Expected Behavior

To work just like tmenu, tnotes and tbm currently behaves.

Detailed Description

The idea is to unify how TinyTools deal with config files. It also allow to dynamically change the base file just by exporting the new file.

As an example from tmenu

$ export TMENU_FILE=quick_menu.yaml; tmenu

Possible Implementation

At the beginning of the script, it's checked if a $TSEARCH_FILE is set on the enviroment

[ ! -f "$TSEARCH_FILE" ] && { echo "No menu file informed!"; exit 1; }