Update project templates

[Wrede]

Severity

• Critical/Blocker (select if the issue makes the application unusable or causes serious data loss)
• High (select if the issue affects a major feature and there is no workaround or the available workaround is very complex)
• Medium (select if the issue affects a minor feature or affects a major feature but has an easy enough workaround to not cause any major inconvenience)
• Low (select if the issue doesn't significantly affect the user experience, like minor visual bugs)

Describe the bug

• fedn-mnist project template do not use fedn images corresponding to pushed images at release in fedn.
• default template contains no images for Dask and ubuntu terminal.

[Wrede]

replaced by #246