[examples] document resuming (#10776)

* document resuming in examples

* fix

* Apply suggestions from code review

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* put trainer code last, adjust notes

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

examples/README.md

@@ -95,6 +95,21 @@ Coming soon!
 | [**`translation`**](https://github.com/huggingface/transformers/tree/master/examples/seq2seq)                       | WMT             | ✅  | - | - | -
 
 
+
+## Resuming training
+
+You can resume training from a previous checkpoint like this:
+
+1. Pass `--output_dir previous_output_dir` without `--overwrite_output_dir` to resume training from the latest checkpoint in `output_dir` (what you would use if the training was interrupted, for instance).
+2. Pass `--model_name_or_path path_to_a_specific_checkpoint` to resume training from that checkpoint folder.
+
+Should you want to turn an example into a notebook where you'd no longer have access to the command
+line, 🤗 Trainer supports resuming from a checkpoint via `trainer.train(resume_from_checkpoint)`.
+
+1. If `resume_from_checkpoint` is `True` it will look for the last checkpoint in the value of `output_dir` passed via `TrainingArguments`.
+2. If `resume_from_checkpoint` is a path to a specific checkpoint it will use that saved checkpoint folder to resume the training from.
+
+
 ## Distributed training and mixed precision
 
 All the PyTorch scripts mentioned above work out of the box with distributed training and mixed precision, thanks to