Add channel/group descriptions

[nicodh]

Needs chatmail/core#7829 to be merged in core

[r10s]

ftr, the "Description" string is meanwhile available as chat_description.

for the info messages, the stock strings DC_STR_GROUP_DESCRIPTION_CHANGED_BY_YOU and DC_STR_GROUP_DESCRIPTION_CHANGED_BY_OTHER must be set to chat_description_changed_by_you resp. chat_description_changed_by_other

and, when tapping the info messages with type=DC_INFO_GROUP_NAME_CHANGED, the profile shall be opened directly; this is the much more probable action the user want to achieve on tapping them.

cmp. deltachat/deltachat-android#4239 and deltachat/deltachat-ios#3020

[nicodh]

The strings are updated but there is still a wrong string
"[Chat description changed. To see this and other new features, please update the app]"
coming from core ( is fixed in chatmail/core#7939 )