apparmor: allow writing .epub files

Currently, exporting document to .epub fails if AppArmor profile is
enabled. This patch fixes it by registering .epub extension within
AppArmor profile.

Change-Id: I5075ac803ffd9157c2f2cc6546895149b0fdd5f2
Reviewed-on: https://gerrit.libreoffice.org/59004
Tested-by: Jenkins
Reviewed-by: Rene Engelhard <rene@debian.org>

sysui/desktop/apparmor/program.soffice.bin

@@ -35,6 +35,8 @@
 @{libreoffice_ext} += [uU][oO][fFtTsSpP]
 #(x)htm(l)
 @{libreoffice_ext} += {,x,X}[hH][tT][mM]{,l,L}
+#.epub
+@{libreoffice_ext} += [eE][pP][uU][bB]
 
 #Images
 @{libreoffice_ext} += [jJ][pP][gG]