Migrated from vue-cli to vite. Also upgraded from vue 2.6 to vue 2.7

[11BelowStudio]

Incompatible with #4 and #6

Seeing as vue-cli is officially in maintenance mode (see vue tooling documentation), and as the specific version of vue-cli within the project was the main reason for #4 in the first place, this PR migrates this project from using vue-cli to using vite - and also migrates from vue 2.6 to 2.7 (which, in turn, might make it easier to migrate to 3 via the vue compat builds)

gonna keep #4 open though in case that hacky workaround is considered preferable