First steps code splitting with Vite 3

[distantnative]

This PR …

Enhancements

• Reduced size of the Panel's vendor JS file by adding code splitting for the vuedraggable.js library

Before

dist/css/style.css   106.29 KiB / gzip: 18.02 KiB
dist/js/index.js     303.70 KiB / gzip: 71.99 KiB
dist/js/vendor.js    375.31 KiB / gzip: 120.69 KiB

After

dist/js/vuedraggable.js   40.74 KiB / gzip: 14.12 KiB 
dist/css/style.css        106.29 KiB / gzip: 18.01 KiB
dist/js/index.js          304.26 KiB / gzip: 72.29 KiB
dist/js/vendor.js         333.99 KiB / gzip: 106.81 KiB

Ready?

• Unit tests for fixed bug/feature
• In-code documentation (wherever needed)
• Tests and checks all pass

For review team

• Add changes to release notes draft in Notion
• Add to website docs release checklist (if needed)

[distantnative]

@afbora did my previous changes cause the problem you just fixed? and we probably should recompile list files then again.

[afbora]

Yes, email mark was throwing error because of email mark has not the editor payload.

[afbora]

Btw are we sure that want to move this changes to 3.7.3? I would favor of 3.7.4 since we already publish releases in short cycles.