Implement "share" menu to share the current project via email, etc.

Description

Impelement "share" menu to share the current project via email, etc. This is similar to what other KDE applications like Okular, Gwenview, Dolphin (and probably more) are already offering. The sharing is possible once the project was saved and there is file that can be shared. sharing

Conformity

• Changelog entry
• Unit tests
• Update INSTALL
• Downport
• Fixes:

When external dependencies are removed

• Reporting to ...