Following the discussion in #6261 it should be possible to load plugin via relative paths, as long as the path starts with `./`.
For example:
```yaml
plugins:
# will load myfirstplugin/plugin.js or myfirstplugin/plugin/index.js
- './myfirstplugin/plugin'
# will load mysecondplugin/plugin.js or mysecondplugin/plugin/index.js
- './mysecondplugin/plugin'
```