DOCS-#3690: Add Slack and paper link to README (#3718)
DOCS-#3690: Add Slack and paper link to README (#3718)

Co-authored-by: Devin Petersohn <e41d922d64ec26f8c15a61d82491163039f96156@users.noreply.github.com>
Signed-off-by: Doris Lee <c110c497f2167bf413e8fff527800e3b9f616b99@gmail.com>

modin-project/modin,modin-project/modin