Plugin to enable line numbers

[tessus]

The dev has to publish to npm. If the dev doesn't do that, there's nothing we can do. Read

Official Joplin plugin repository is now ready! If you are developing a plugin please read on

Following this discussion, it was eventually decided to leverage npmjs package repository to publish Joplin plugins. Then a script is used to fetch these plugins and move them to the official plugin repository: This repository will then be used to load the list of plugins in the main app, and install and update them directly. If you are a plugin developer, please consider running yo joplin --update from the root of your repository, and let me know if you notice any issue. Once that's done, y…