chore: import upstream snapshot with attribution

extra/example_data/ner_example_data/README.md

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+## Examples of NER/IOB data that can be converted with `spacy convert`
+
+To convert an IOB file to `.spacy` ([`DocBin`](https://spacy.io/api/docbin))
+for spaCy v3:
+
+```bash
+python -m spacy convert -c iob -s -n 10 -b en_core_web_sm file.iob .
+```
+
+See all the `spacy convert` options: https://spacy.io/api/cli#convert
+
+---
+
+The spaCy v2 JSON training files were generated using **spaCy v2** with:
+
+```bash
+python -m spacy convert -c iob -s -n 10 -b en file.iob
+```
+
+To convert an existing JSON training file to `.spacy` for spaCy v3, convert
+with **spaCy v3**:
+
+```bash
+python -m spacy convert file.json .
+```