Added menu and simplified workflow

What's Changed

This has a simplified selection process at the beginning to

• Menu workflow by @TrezorHannes in #2
• define the direction
• chose one of the 3 fee-options
• set the value for the appropriate option
• Additionally set an umbrel detection environment

New Contributors

• @TrezorHannes made their first contribution in #2

Full Changelog: https://github.com/TrezorHannes/bash-rebalancer/commits/v0.2.1