V7 branch now in master!

[jfhenon]

While we still have a lot of work to make V7 complete, we made most of the reorganisation of the code and introduction of new packages.

This is now that you can help with your contributions!

What is V7:

• It's a brand new look (all images were turned to SVG... obviously)
• it's many updates to dependencies (i.e. addresses many security issues)
• Continuous integration has been setup with cypress tests (will help to review contributions)

What is still to be checked or changed:

• We still need some efforts to remove jQuery -> help needed: track remaining jQuery usage and move to native DOM functions.
• I18next has introduced for localization but we need to move all "strings" to their keys (and there is still a bug to change the language) -> help needed
• We use Web components (but maybe we should use React/View in the long run or at least a package such as https://lit.dev/
• Most HTML code as well as CSS are now imbedded directly in the code. This is going to be convenient for a simpler packaging of svgedit but this also complexifies some aspect of customization.
• Linter rules could be made tighter.
• Some plugins needs to be migrated and tested to work with V7
• the documentation needs to be updated
• and many other things...