advotracker-db: introduce new submodule

* orign: https://gitea.networkx.de:50443/rzerres/advotracker.db
* for now, we do have a Microsoft CA which isn't handled as an
  official CA.
  You need to exclude SSL verification to push/pull/clone like this:

* # git config  --file .git/modules/advotracker-db/config --list
* # git config --file .git/modules/advotracker-db/config  http.https://gitea.networkx.de:50443.sslverify false

* # git -c http.https://gitea.networkx.de:50443.sslverify=false submodule add  https://gitea.networkx.de:50443/rzerres/advotracker-db

Signed-off-by: Ralf Zerres <ralf.zerres@networkx.de>

.gitmodules

@@ -4,3 +4,6 @@
 [submodule "backend"]
 	path = backend
 	url = ./backend/
+[submodule "advotracker-db"]
+	path = advotracker-db
+	url = https://gitea.networkx.de:50443/rzerres/advotracker-db