feat: Supports using Python language to extend PPE language instructions.

[snowyu]

Inline python function to extend instruction:

- !fn |-
    [python] def add(a,b):
      return a+b
- $add(1,2)

Import python functions from file:

---
import: "./my.py"
---
- $add(1,2)

# my.py
def add(a,b):
  return a+b