Add remote desktop via /desktop path, and qgis

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This is meant to make a /desktop path available just like the /lab path is available. In case it works, perhaps the application qgis is available as well. Let's see.

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I ran into issues installing qgis using the latest pangeo-notebook tag that has bumped to ubuntu:21.10 as a base image. I made a note about it and reverted to use a previous pangeo-notebook tag that still used ubuntu:20.04.

Related PR: https://github.com/pangeo-data/pangeo-docker-images/pull/221

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Error using the base image ubuntu 21.10 and specifying focal (ubutnu 20.04) when trying to install qgis that isn't published for ubuntu 21.10 (named impish)

gpg: keyring '/etc/apt/trusted.gpg.d/qgis-archive.gpg' created
gpg: key F7E06F06199EF2F2: 1 signature not checked due to a missing key
gpg: directory '/home/jovyan/.gnupg' created
gpg: /home/jovyan/.gnupg/trustdb.gpg: trustdb created
gpg: key F7E06F06199EF2F2: public key "QGIS Archive Automatic Signing Key (2020) <qgis-developer@lists.osgeo.org>" imported
gpg: Total number processed: 1
gpg:               imported: 1
gpg: no ultimately trusted keys found
Get:1 http://security.ubuntu.com/ubuntu impish-security InRelease [90.7 kB]
Get:2 http://archive.ubuntu.com/ubuntu impish InRelease [269 kB]
Get:3 https://qgis.org/ubuntu focal InRelease [2731 B]
Get:4 http://archive.ubuntu.com/ubuntu impish-updates InRelease [90.7 kB]
Get:5 http://archive.ubuntu.com/ubuntu impish-backports InRelease [90.7 kB]
Get:6 http://archive.ubuntu.com/ubuntu impish/restricted amd64 Packages [114 kB]
Get:7 http://archive.ubuntu.com/ubuntu impish/main amd64 Packages [1807 kB]
Get:8 https://qgis.org/ubuntu focal/main amd64 Packages [25.3 kB]
Get:9 http://archive.ubuntu.com/ubuntu impish/universe amd64 Packages [16.9 MB]
Get:10 http://archive.ubuntu.com/ubuntu impish/multiverse amd64 Packages [263 kB]
Fetched 19.6 MB in 2s (8290 kB/s)
Reading package lists...
Repository: 'deb https://qgis.org/ubuntu focal main'
Description:
Archive for codename: focal components: main
More info: https://qgis.org/ubuntu
Adding repository.
Adding deb entry to /etc/apt/sources.list.d/archive_uri-https_qgis_org_ubuntu-impish.list
Adding disabled deb-src entry to /etc/apt/sources.list.d/archive_uri-https_qgis_org_ubuntu-impish.list
E: Unable to correct problems, you have held broken packages.
The command '/bin/sh -c wget -qO - https://qgis.org/downloads/qgis-2020.gpg.key   | gpg --no-default-keyring --keyring gnupg-ring:/etc/apt/trusted.gpg.d/qgis-archive.gpg --import  && chmod a+r /etc/apt/trusted.gpg.d/qgis-archive.gpg  && add-apt-repository "deb https://qgis.org/ubuntu focal main"  && apt-get -y update > /dev/null  && apt-get -y install         qgis         qgis-plugin-grass     > /dev/null  && rm -rf /var/lib/apt/lists/*' returned a non-zero code: 100