Feature Request: Update the farm module to farm only specified crops

## Describe your suggestion
It would be incredibly useful if you could direct the farming mod on baritone to farm specific crops in the same manner that you are able direct the auto-mine mod to mine only specific ores.

## Context
This feature would prevent the farm module from planting crops in the wrong area which can be a problem.

The issue names Baritone’s farm and auto-mine modules but no files or tests. Start by locating those modules and comparing how auto-mine restricts work to specified ores. Define how crop selection should be provided, then verify that farming affects only the selected crops and avoids planting in the wrong area.

Written by the indexing model from the issue text.