Update index.md (rms-open-letter#23)

Added Chris DiBona and David Turner

Co-authored-by: Elana Hashman <[email protected]>

Author: Molly de Blanc

index.md

@@ -59,4 +59,6 @@ Signed,
 - Daniel Soskel
 - Tony Colston
 - Neil Watson (Former CFEngine Community Advisory Board Member)
+- Chris DiBona (Google LLC.)
+- David Turner (former GPL Compliance Engineer at FSF)
 - Ignacio Torres Masdeu