Support for Spark 3.2

[lhendra]

Great library, but we need an official version for Spark 3.2. Thanks!

[erikerlandson]

xref: #26

[erikerlandson]

I have published:

"org.isarnproject" %% "isarn-sketches-spark" % "0.6.0-RC1-sp3.2"

Let me know how this works for you - if it is satisfactory, I can publish an official release

cc @lhendra @HelenParr

[lhendra]

@erikerlandson Tested the new RC and it worked very well!