List csvdiff under alternatives

Refs https://twitter.com/schwanksta/status/1553101581255573507

Author: simonw

README.md

@@ -125,4 +125,8 @@ If the columns in the CSV have changed, those added or removed columns will be i
 
 Suppose current directory contains two csv files : one.csv two.csv
 
-    $ docker run --rm -v $(pwd):/files csvdiff one.csv two.csv
+    $ docker run --rm -v $(pwd):/files csvdiff one.csv two.csv
+    
+## Alternatives
+
+- [csvdiff](https://github.com/aswinkarthik/csvdiff) is a "fast diff tool for comparing CSV files" - you may get better results from this than from `csv-diff` against larger files.