Option to upgrade the script from the CLI

It should be interesting to develop a mechanism to upgrade ExTldr, at least the script. One idea might be to compare the version of ExTldr used by the user with the latest release available in GitHub. If the release would be newer, it will upgrade the ExTldr, but if the release is pre-release, an alpha version, ¿or beta?, should ask the user if he still wants to upgrade ExTldr.