Improve dataset card: Clarify name, add license and link to Github repo

This PR updates the dataset card for the Library of Congress dataset to:

* Clarify that it's a subset of the Common Pile by updating the `pretty_name`.
* Adds the license information (cc-by-4.0).
* Adds a link to the Github repository

README.md

@@ -1,15 +1,18 @@
 ---
-task_categories:
-- text-generation
 language:
 - en
-pretty_name: Library of Congress
+task_categories:
+- text-generation
+pretty_name: Library of Congress (subset of Common Pile)
+license: cc-by-4.0
 ---
-# Library of Congress
+
+# Library of Congress (subset of Common Pile)
 
 ## Description
 The Library of Congress (LoC) curates a collection of public domain books called ["Selected Digitized Books"](https://www.loc.gov/collections/selected-digitized-books/). 
 We have downloaded over 130,000 English-language books from this public domain collection as OCR plain text files using the [LoC APIs](https://www.loc.gov/apis/).
+This dataset is a subset of the Common Pile v0.1. For more information, see [The Common Pile v0.1 paper](https://huggingface.co/papers/2506.05209).
 
 ## Dataset Statistics
 | Documents | UTF-8 GB |
@@ -17,8 +20,10 @@ We have downloaded over 130,000 English-language books from this public domain c
 | 135,500 | 47.8 |
 
 ## License Issues
-While we aim to produce datasets with completely accurate licensing information, license laundering and inaccurate metadata can cause us to erroneously assign the incorrect license to some documents (for further discussion of this limitation, please see [our paper](https://huggingface.co/papers/2506.05209)). If you believe you have found an instance of incorrect licensing in this dataset, please [start a discussion](https://github.com/r-three/common-pile/discussions/new) on this repository. 
+While we aim to produce datasets with completely accurate licensing information, license laundering and inaccurate metadata can cause us to erroneously assign the incorrect license to some documents (for further discussion of this limitation, please see [our paper](https://huggingface.co/papers/2506.05209)). If you believe you have found an instance of incorrect licensing in this dataset, please [start a discussion](https://github.com/r-three/common-pile/discussions/new) on this repository.
+The overall license for this dataset is intended to be CC-BY-4.0, but this is not a guarantee for individual documents within the dataset.
 
+Github: https://github.com/r-three/common-pile
 
 ## Other Versions
 This is the "raw" version of the Library of Congress dataset.