* Warns user if trying to disable a plugin that is already
enabled when doing `config.plugins.plugin_name = false` and also
prevents replacing the current plugin config table with the false
value to mitigate runtime issues.
* Uses a merge strategy by default when assigning a table to a plugin
config to prevent a user from removing a plugin default config values
as experienced and explained on this issue lite-xl-plugins#158
* This change is basically backwards compatible, but will require a
change on the settings ui plugin on how it checks for already
enabled plugins, since rawget will no longer be a working hack
or workaround for this.
* As suggested by Adam dropped loaded key and switched to package.loaded
6925c06599