Update README to reflect CCC20 Extension (#1261)

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>
(cherry picked from commit a301fa1)

Author: mergify[bot]

README.md

@@ -6,7 +6,8 @@
 
 [The 3rd Chisel Community Conference (hosted by CHIPS Alliance) is happening on January 29--30, 2020!](https://events.linuxfoundation.org/chisel-community-conference/)
 
-We're [accepting talk proposals](https://events.linuxfoundation.org/chisel-community-conference/program/cfp/) for submissions through November 26th.
+We're [accepting talk proposals](https://events.linuxfoundation.org/chisel-community-conference/program/cfp/) for through December 12th.
+(*Acceptances are rolling, so if you have travel/visa requirements, get your submissions in!*)
 
 Make sure to [register](https://events.linuxfoundation.org/chisel-community-conference/register/) and attend to meet some other Chisel-ers and FIRRTL-ers!