Import wiki documents to SDG

docs/sdg/wiki-doc-source.md

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+# Wiki document source
+
+Fetching information from wikis is an essential
+feature for fine-tuning LLMs on public knowledge.
+
+## Interfaces
+
+qna.yaml file, `document` section:
+
+- Wiki Host: The base URL of a wiki host.
+- Page titles: The titles of the Wiki pages to fetch.
+- oldid: IDs of old releases.
+
+The qna.yaml file can define single host and multiple spaces and pages,
+each with an optional version.
+
+Example of fetch URL:
+
+- https://en.wikipedia.org/w/index.php?title=IBM_Granite&oldid=1235007056&action=raw
+
+Note that oldid is sufficient to reterieve a page:
+
+- https://en.wikipedia.org/w/index.php?oldid=1235007056&action=raw
+
+Page title is used for vaidation.
+
+## Changes across modules
+
+- [Schema module](https://github.com/instructlab/schema) defines the structure and validation rules for
+  the qna.yaml file.
+- [SDG taxonomy module](https://github.com/instructlab/sdg/blob/main/src/instructlab/sdg/utils/taxonomy.py)
+  fetches documents
+- [SDG unit tests](https://github.com/instructlab/sdg/tree/main/tests)
+
+## Additional External Packages
+
+- urllib
+