Update stable version in readme and add changelog

Author: jeherve

readme.txt

@@ -1,7 +1,7 @@
 === Jetpack by WordPress.com ===
 Contributors: automattic, adamkheckler, aduth, akirk, allendav, alternatekev, andy, annezazu, apeatling, azaozz, batmoo, barry, beaulebens, blobaugh, brbrr, cainm, cena, cfinke, chaselivingston, chellycat, clickysteve, csonnek, danielbachhuber, davoraltman, daniloercoli, delawski, designsimply, dllh, drawmyface, dsmart, dzver, ebinnion, egregor, eliorivero, enej, eoigal, erania-pinnera, ethitter, gcorne, georgestephanis, gibrown, goldsounds, hew, hugobaeta, hypertextranch, iammattthomas, iandunn, jblz, jasmussen, jeffgolenski, jeherve, jenhooks, jenia, jessefriedman, jgs, jkudish, jmdodd, joanrho, johnjamesjacoby, jshreve, kbrownkd, keoshi, koke, kraftbj, lancewillett, lschuyler, macmanx, martinremy, matt, matveb, mattwiebe, maverick3x6, mcsf, mdawaffe, MichaelArestad, migueluy, mikeyarce, mkaz, nancythanki, nickmomrik, obenland, oskosk, pento, professor44, rachelsquirrel, rdcoll, ryancowles, richardmuscat, richardmtl, roccotripaldi, samhotchkiss, scarstocea, scottsweb, sdquirk, simison, stephdau, tmoorewp, tyxla, Viper007Bond, westi, yoavf, zinigor
 Tags: Jetpack, WordPress.com, backup, security, related posts, CDN, speed, anti-spam, social sharing, SEO, video, stats
-Stable tag: 8.4
+Stable tag: 8.4.1
 Requires at least: 5.3
 Requires PHP: 5.6
 Tested up to: 5.4
@@ -96,6 +96,14 @@ There are opportunities for developers at all levels to contribute. [Learn more
 
 == Changelog ==
 
+= 8.4.1 =
+
+* Release date: April 7, 2020
+
+**Bug Fixes**
+
+* Secure Sign On: fix conflict that would block one from logging in to their site via the Secure Sign On option.
+
 = 8.4 =
 
 * Release date: April 7, 2020