separate svgcanvas from svgedit

now you can use directlt svgcanvas. see readme.md

* configure workspaces
* move svgcanvas to packages folder
* move utils to common and paint to svgcanvas
* make svgcanvas a dependency of svgedit
* update deps
* workspaces requires npm 7 at least so the ci needs a new node version
* update github actions to V3
* update snapshots using custom svg exports
* remove unmaintained cypress snapshot plugin
* new github action to add coverage in PR
* Update onpushandpullrequest.yml
* svgcanvas v7.1.6

src/editor/dialogs/imagePropertiesDialog.js

@@ -1,8 +1,10 @@
 
+import SvgCanvas from '@svgedit/svgcanvas'
 /* globals svgEditor */
-import { isValidUnit } from '../../common/units.js'
 import imagePropertiesDialogHTML from './imagePropertiesDialog.html'
 
+const { isValidUnit } = SvgCanvas
+
 const template = document.createElement('template')
 template.innerHTML = imagePropertiesDialogHTML
 /**