v4.2.0-preview3
[SPARK-29052][DOCS][ML][PYTHON][CORE][R][SQL][SS] Create a Migration Guide tap in Spark documentation
[SPARK-25584][ML][DOC] datasource for libsvm user guide
[MINOR][DOCS] Fix various broken links and link anchors
[SPARK-54576][SQL] Add documentation for new Datasketches-based aggregate functions
[SPARK-49378][DOCS][SS] Break apart the Structured Streaming Programming Guide