feat: webxdc notify (#6230)

this PR adds support for the property `update.notify` to notify about
changes in `update.info` or `update.summary`. the property can be set to
an array of addresses [^1]

core emits then the event `IncomingWebxdcNotify`, resulting in all UIs
to display a system notification, maybe even via PUSH.

for using the existing `update.info` and `update.summary`: the message
is no secret and should be visible to all group members as usual, to not
break the UX of having same group messages on all devices of all users -
as known already from the normal messages.

also, that way, there is no question what happens if user have disabled
notifications as the change is presented in the chat as well

doc counterpart at https://github.com/webxdc/website/pull/90

closes #6217 

[^1]: addresses come in either via the payload as currently or as an
explicit sender in the future - this does not affect this PR. same for
translations, see discussions at #6217 and #6097

---------

Co-authored-by: adb <asieldbenitez@gmail.com>
Co-authored-by: l <link2xt@testrun.org>

node/lib/constants.ts

@@ -52,6 +52,7 @@ export enum C {
   DC_EVENT_INCOMING_MSG = 2005,
   DC_EVENT_INCOMING_MSG_BUNCH = 2006,
   DC_EVENT_INCOMING_REACTION = 2002,
+  DC_EVENT_INCOMING_WEBXDC_NOTIFY = 2003,
   DC_EVENT_INFO = 100,
   DC_EVENT_LOCATION_CHANGED = 2035,
   DC_EVENT_MSGS_CHANGED = 2000,
@@ -325,6 +326,7 @@ export const EventId2EventName: { [key: number]: string } = {
   2000: 'DC_EVENT_MSGS_CHANGED',
   2001: 'DC_EVENT_REACTIONS_CHANGED',
   2002: 'DC_EVENT_INCOMING_REACTION',
+  2003: 'DC_EVENT_INCOMING_WEBXDC_NOTIFY',
   2005: 'DC_EVENT_INCOMING_MSG',
   2006: 'DC_EVENT_INCOMING_MSG_BUNCH',
   2008: 'DC_EVENT_MSGS_NOTICED',