docs: `PDBDebugger` and `Parallelizable`

It should be noted the `PDBDebugger` doesn't work with parallel and multithreaded task-based execution. However, you can use it in combination with the `SynchronousLocalTaskExecutor`

```python
import my_dataflow
from hamilton import driver
from hamilton.execution.executors import SynchronousLocalTaskExecutors
from hamilton.lifecycle import PDBDebugger

dr = (
driver.Builder()
.enable_dynamic_execution(allow_experimental_mode=True)
.with_modules(my_dataflow)
.with_adapters(PDBDebugger(...))
.with_remote_executor(SynchronousLocalTaskExecutor())
.build()
)

dr.execute(...)
```