Add splitterm plugin

[lukhof]

Add splitterm plugin, a plugin which lets you run python/bash/perl code in a new split terminal. You can select portions of the code or run the whole file (if nothing is selected).

[taconi]

Hello, could you update the PR to resolve the conflicts?

Another issue is that your repo.json does not have the and License field, could you add this metadata?

Could you add your repo.json to the plugins/ folder and update channel.json link to use this link?
E.g. https://raw.githubusercontent.com/micro-editor/plugin-channel/master/plugins/editorconfig-micro.json.
Use the plugin name as the file name.

It was missing from the README.md table, could you solve this?