feat: add variable swapping one-liner to python_oneliners.md

@@ -179,3 +179,9 @@ transposed = [list(row) for row in zip(*matrix)]

merged_dict = dict(zip(keys, values))

```

**Example:** `keys=['a', 'b'], values=[1, 2] → {'a': 1, 'b': 2}`

## Swap two variables without a temporary one

```python

a, b = b, a

```

**Example:** `a=5, b=10 → a=10, b=5`