nextcloud: update skeleton files, use logo with dot,

add useful links to Readme and Example ODT.

Note that currently these skeleton files have to be manually uploaded to
/var/lib/nextcloud/skeleton on nachtigall.

modules/nextcloud/nextcloud-skeleton/Pictures/pubsolar.svg

@@ -4,7 +4,7 @@
    data-name="Layer 3"
    viewBox="0 0 275.3 276.37"
    version="1.1"
-   sodipodi:docname="pubsolar.svg"
+   sodipodi:docname="pub.solar.svg"
    inkscape:version="1.1.2 (0a00cf5339, 2022-02-04)"
    xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
    xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"

modules/nextcloud/nextcloud-skeleton/Readme.md

@@ -2,6 +2,10 @@
 
 By default, the cloud is limited to 10MB of storage. If you want more, just send a short request to [crew@pub.solar](mailto:crew@pub.solar).
 
-To download a desktop client, go to https://nextcloud.com/download.
+To download a Nextlcoud desktop client, go to https://nextcloud.com/download.
 
 You can edit this file by clicking here, and put any contents you want as notes for this directory :)
+
+Other useful links:
+- pub.solar Wiki https://wiki.pub.solar
+- Our Website https://pub.solar